diff --git a/c++/carla-backend/carla_backend.h b/c++/carla-backend/carla_backend.h
index d23c2c3..909ae9d 100644
--- a/c++/carla-backend/carla_backend.h
+++ b/c++/carla-backend/carla_backend.h
@@ -51,14 +51,15 @@ const unsigned int MAX_PARAMETERS = 200; //!< Default value for the maximum numb
  * \see CarlaPlugin::hints()
  * @{
  */
-const unsigned int PLUGIN_IS_BRIDGE          = 0x01; //!< Plugin is a bridge (ie, BridgePlugin). This hint is required because "bridge" itself is not a plugin type.
-const unsigned int PLUGIN_IS_SYNTH           = 0x02; //!< Plugin is a synthesizer (produces sound).
-const unsigned int PLUGIN_HAS_GUI            = 0x04; //!< Plugin has its own custom GUI.
-const unsigned int PLUGIN_USES_CHUNKS        = 0x08; //!< Plugin uses chunks to save internal data.\see CarlaPlugin::chunkData()
-const unsigned int PLUGIN_USES_SINGLE_THREAD = 0x10; //!< Plugin has its own custom GUI.
-const unsigned int PLUGIN_CAN_DRYWET         = 0x20; //!< Plugin can make use of Dry/Wet controls.
-const unsigned int PLUGIN_CAN_VOLUME         = 0x40; //!< Plugin can make use of Volume controls.
-const unsigned int PLUGIN_CAN_BALANCE        = 0x80; //!< Plugin can make use of Left & Right Balance controls.
+const unsigned int PLUGIN_IS_BRIDGE          = 0x001; //!< Plugin is a bridge (ie, BridgePlugin). This hint is required because "bridge" itself is not a plugin type.
+const unsigned int PLUGIN_IS_SYNTH           = 0x002; //!< Plugin is a synthesizer (produces sound).
+const unsigned int PLUGIN_HAS_GUI            = 0x004; //!< Plugin has its own custom GUI.
+const unsigned int PLUGIN_USES_CHUNKS        = 0x008; //!< Plugin uses chunks to save internal data.\see CarlaPlugin::chunkData()
+const unsigned int PLUGIN_USES_SINGLE_THREAD = 0x010; //!< Plugin has its own custom GUI.
+const unsigned int PLUGIN_CAN_DRYWET         = 0x020; //!< Plugin can make use of Dry/Wet controls.
+const unsigned int PLUGIN_CAN_VOLUME         = 0x040; //!< Plugin can make use of Volume controls.
+const unsigned int PLUGIN_CAN_BALANCE        = 0x080; //!< Plugin can make use of Left & Right Balance controls.
+const unsigned int PLUGIN_CAN_FORCE_STEREO   = 0x100; //!< Plugin can be used in forced-stereo mode.
 /**@}*/
 
 /*!
diff --git a/c++/carla-backend/carla_native.cpp b/c++/carla-backend/carla_native.cpp
index 7726bd1..3401ddc 100644
--- a/c++/carla-backend/carla_native.cpp
+++ b/c++/carla-backend/carla_native.cpp
@@ -78,8 +78,8 @@ public:
 
         m_type = PLUGIN_INTERNAL;
 
-        descriptor = nullptr;
-        handle     = nullptr;
+        descriptor  = nullptr;
+        handle = h2 = nullptr;
 
         host.handle = this;
         host.get_buffer_size  = carla_host_get_buffer_size;
@@ -103,16 +103,16 @@ public:
             {
                 if (handle)
                     descriptor->deactivate(handle);
-                //if (h2)
-                //    descriptor->deactivate(h2);
+                if (h2)
+                    descriptor->deactivate(h2);
             }
 
             if (descriptor->cleanup)
             {
                 if (handle)
                     descriptor->cleanup(handle);
-                //if (h2)
-                //    descriptor->cleanup(h2);
+                if (h2)
+                    descriptor->cleanup(h2);
             }
         }
     }
@@ -688,7 +688,7 @@ public:
         param.count = params;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         if (aOuts > 0 && (aIns == aOuts || aIns == 1))
             m_hints |= PLUGIN_CAN_DRYWET;
@@ -699,6 +699,9 @@ public:
         if (aOuts >= 2 && aOuts%2 == 0)
             m_hints |= PLUGIN_CAN_BALANCE;
 
+        if (aIns <= 2 && aOuts <= 2 && (aIns == aOuts || aIns == 0 || aOuts == 0) && mIns <= 1 && mOuts <= 1)
+            m_hints |= PLUGIN_CAN_FORCE_STEREO;
+
         m_hints |= getPluginHintsFromNative(descriptor->hints);
 
         reloadPrograms(true);
@@ -1561,7 +1564,7 @@ public:
 
 private:
     const PluginDescriptor* descriptor;
-    PluginHandle handle;
+    PluginHandle handle, h2;
     HostDescriptor host;
 
     bool isProcessing;
@@ -1598,6 +1601,17 @@ CarlaPlugin* CarlaPlugin::newNative(const initializer& init)
     }
 
     plugin->reload();
+
+    if (carlaOptions.processMode == PROCESS_MODE_CONTINUOUS_RACK)
+    {
+        if (! plugin->hints() & PLUGIN_CAN_FORCE_STEREO)
+        {
+            setLastError("Carla's rack mode can only work with Mono or Stereo Internal plugins, sorry!");
+            delete plugin;
+            return nullptr;
+        }
+    }
+
     plugin->registerToOsc();
 
     return plugin;
diff --git a/c++/carla-backend/dssi.cpp b/c++/carla-backend/dssi.cpp
index 30fa620..0d82725 100644
--- a/c++/carla-backend/dssi.cpp
+++ b/c++/carla-backend/dssi.cpp
@@ -671,7 +671,7 @@ public:
         param.count = params;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         if (midi.portMin && aOut.count > 0)
             m_hints |= PLUGIN_IS_SYNTH;
@@ -693,6 +693,9 @@ public:
         if (aOuts >= 2 && aOuts%2 == 0)
             m_hints |= PLUGIN_CAN_BALANCE;
 
+        if (aIns <= 2 && aOuts <= 2 && (aIns == aOuts || aIns == 0 || aOuts == 0))
+            m_hints |= PLUGIN_CAN_FORCE_STEREO;
+
         reloadPrograms(true);
 
         x_client->activate();
@@ -1552,10 +1555,7 @@ CarlaPlugin* CarlaPlugin::newDSSI(const initializer& init, const void* const ext
 #ifndef BUILD_BRIDGE
     if (carlaOptions.processMode == PROCESS_MODE_CONTINUOUS_RACK)
     {
-        const uint32_t ins  = plugin->audioInCount();
-        const uint32_t outs = plugin->audioOutCount();
-
-        if (ins > 2 || outs > 2 || (ins != outs && ins != 0 && outs != 0))
+        if (! plugin->hints() & PLUGIN_CAN_FORCE_STEREO)
         {
             setLastError("Carla's rack mode can only work with Mono or Stereo DSSI plugins, sorry!");
             delete plugin;
diff --git a/c++/carla-backend/fluidsynth.cpp b/c++/carla-backend/fluidsynth.cpp
index 697806c..5a22f4c 100644
--- a/c++/carla-backend/fluidsynth.cpp
+++ b/c++/carla-backend/fluidsynth.cpp
@@ -716,11 +716,12 @@ public:
         param.count = params;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         m_hints |= PLUGIN_IS_SYNTH;
         m_hints |= PLUGIN_CAN_VOLUME;
         m_hints |= PLUGIN_CAN_BALANCE;
+        m_hints |= PLUGIN_CAN_FORCE_STEREO;
 
         reloadPrograms(true);
 
diff --git a/c++/carla-backend/ladspa.cpp b/c++/carla-backend/ladspa.cpp
index cd6f016..870da60 100644
--- a/c++/carla-backend/ladspa.cpp
+++ b/c++/carla-backend/ladspa.cpp
@@ -651,7 +651,7 @@ public:
         param.count = params;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         if (aOuts > 0 && (aIns == aOuts || aIns == 1))
             m_hints |= PLUGIN_CAN_DRYWET;
@@ -662,6 +662,9 @@ public:
         if (aOuts >= 2 && aOuts%2 == 0)
             m_hints |= PLUGIN_CAN_BALANCE;
 
+        if (aIns <= 2 && aOuts <= 2 && (aIns == aOuts || aIns == 0 || aOuts == 0))
+            m_hints |= PLUGIN_CAN_FORCE_STEREO;
+
         x_client->activate();
 
         qDebug("LadspaPlugin::reload() - end");
@@ -1160,10 +1163,7 @@ CarlaPlugin* CarlaPlugin::newLADSPA(const initializer& init, const void* const e
 #ifndef BUILD_BRIDGE
     if (carlaOptions.processMode == PROCESS_MODE_CONTINUOUS_RACK)
     {
-        const uint32_t ins  = plugin->audioInCount();
-        const uint32_t outs = plugin->audioOutCount();
-
-        if (ins > 2 || outs > 2 || (ins != outs && ins != 0 && outs != 0))
+        if (! plugin->hints() & PLUGIN_CAN_FORCE_STEREO)
         {
             setLastError("Carla's rack mode can only work with Mono or Stereo LADSPA plugins, sorry!");
             delete plugin;
diff --git a/c++/carla-backend/linuxsampler.cpp b/c++/carla-backend/linuxsampler.cpp
index 2d34209..5b8baa6 100644
--- a/c++/carla-backend/linuxsampler.cpp
+++ b/c++/carla-backend/linuxsampler.cpp
@@ -199,11 +199,12 @@ public:
         aOut.count  = aOuts;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         m_hints |= PLUGIN_IS_SYNTH;
         m_hints |= PLUGIN_CAN_VOLUME;
         m_hints |= PLUGIN_CAN_BALANCE;
+        m_hints |= PLUGIN_CAN_FORCE_STEREO;
 
         reloadPrograms(true);
 
diff --git a/c++/carla-backend/lv2.cpp b/c++/carla-backend/lv2.cpp
index 7d99abe..3274bdd 100644
--- a/c++/carla-backend/lv2.cpp
+++ b/c++/carla-backend/lv2.cpp
@@ -54,9 +54,9 @@ const unsigned int MAX_EVENT_BUFFER = 8192; // 0x2000
  * @defgroup PluginHints Plugin Hints
  * @{
  */
-const unsigned int PLUGIN_HAS_EXTENSION_PROGRAMS = 0x100; //!< LV2 Plugin has Programs extension
-const unsigned int PLUGIN_HAS_EXTENSION_STATE    = 0x200; //!< LV2 Plugin has State extension
-const unsigned int PLUGIN_HAS_EXTENSION_WORKER   = 0x400; //!< LV2 Plugin has Worker extension
+const unsigned int PLUGIN_HAS_EXTENSION_PROGRAMS = 0x1000; //!< LV2 Plugin has Programs extension
+const unsigned int PLUGIN_HAS_EXTENSION_STATE    = 0x2000; //!< LV2 Plugin has State extension
+const unsigned int PLUGIN_HAS_EXTENSION_WORKER   = 0x4000; //!< LV2 Plugin has Worker extension
 /**@}*/
 
 /*!
@@ -1144,8 +1144,25 @@ public:
                 params += 1;
         }
 
+        // check extensions
+        ext.state      = nullptr;
+        ext.worker     = nullptr;
+        ext.programs   = nullptr;
+
+        if (descriptor->extension_data)
+        {
+            if (m_hints & PLUGIN_HAS_EXTENSION_PROGRAMS)
+                ext.programs = (const LV2_Programs_Interface*)descriptor->extension_data(LV2_PROGRAMS__Interface);
+
+            if (m_hints & PLUGIN_HAS_EXTENSION_STATE)
+                ext.state = (const LV2_State_Interface*)descriptor->extension_data(LV2_STATE__interface);
+
+            if (m_hints & PLUGIN_HAS_EXTENSION_WORKER)
+                ext.worker = (const LV2_Worker_Interface*)descriptor->extension_data(LV2_WORKER__interface);
+        }
+
 #ifndef BUILD_BRIDGE
-        if (carlaOptions.forceStereo && (aIns == 1 || aOuts == 1) && ! h2)
+        if (carlaOptions.forceStereo && (aIns == 1 || aOuts == 1) && ! (h2 || ext.state || ext.worker))
         {
             h2 = descriptor->instantiate(descriptor, sampleRate, rdf_descriptor->Bundle, features);
 
@@ -1678,7 +1695,7 @@ public:
         param.count = params;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         if (LV2_IS_GENERATOR(rdf_descriptor->Type))
             m_hints |= PLUGIN_IS_SYNTH;
@@ -1692,21 +1709,15 @@ public:
         if (aOuts >= 2 && aOuts%2 == 0)
             m_hints |= PLUGIN_CAN_BALANCE;
 
-        // check extensions
-        ext.state      = nullptr;
-        ext.worker     = nullptr;
-        ext.programs   = nullptr;
-
-        if (descriptor->extension_data)
+        if (ext.state || ext.worker)
         {
-            if (m_hints & PLUGIN_HAS_EXTENSION_PROGRAMS)
-                ext.programs = (const LV2_Programs_Interface*)descriptor->extension_data(LV2_PROGRAMS__Interface);
-
-            if (m_hints & PLUGIN_HAS_EXTENSION_STATE)
-                ext.state = (const LV2_State_Interface*)descriptor->extension_data(LV2_STATE__interface);
-
-            if (m_hints & PLUGIN_HAS_EXTENSION_WORKER)
-                ext.worker = (const LV2_Worker_Interface*)descriptor->extension_data(LV2_WORKER__interface);
+            if ((aIns == 0 || aIns == 2) && (aOuts == 0 || aOuts == 2) && evIn.count <= 1 && evOut.count <= 1)
+                m_hints |= PLUGIN_CAN_FORCE_STEREO;
+        }
+        else
+        {
+            if (aIns <= 2 && aOuts <= 2 && (aIns == aOuts || aIns == 0 || aOuts == 0) && evIn.count <= 1 && evOut.count <= 1)
+                m_hints |= PLUGIN_CAN_FORCE_STEREO;
         }
 
         reloadPrograms(true);
@@ -4495,12 +4506,9 @@ CarlaPlugin* CarlaPlugin::newLV2(const initializer& init)
 #ifndef BUILD_BRIDGE
     if (carlaOptions.processMode == PROCESS_MODE_CONTINUOUS_RACK)
     {
-        const uint32_t ins  = plugin->audioInCount();
-        const uint32_t outs = plugin->audioOutCount();
-
-        if (ins > 2 || outs > 2 || (ins != outs && ins != 0 && outs != 0))
+        if (! plugin->hints() & PLUGIN_CAN_FORCE_STEREO)
         {
-            setLastError("Carla's rack mode can only work with Mono or Stereo LV2 plugins, sorry!");
+            setLastError("Carla's rack mode can only work with Mono (simple) or Stereo LV2 plugins, sorry!");
             delete plugin;
             return nullptr;
         }
diff --git a/c++/carla-backend/vst.cpp b/c++/carla-backend/vst.cpp
index 98cba2e..887d03a 100644
--- a/c++/carla-backend/vst.cpp
+++ b/c++/carla-backend/vst.cpp
@@ -38,10 +38,10 @@ CARLA_BACKEND_START_NAMESPACE
  * @defgroup PluginHints Plugin Hints
  * @{
  */
-const unsigned int PLUGIN_CAN_PROCESS_REPLACING = 0x100; //!< VST Plugin cas use processReplacing()
-const unsigned int PLUGIN_HAS_COCKOS_EXTENSIONS = 0x200; //!< VST Plugin has Cockos extensions
-const unsigned int PLUGIN_USES_OLD_VSTSDK       = 0x400; //!< VST Plugin uses an old VST SDK
-const unsigned int PLUGIN_WANTS_MIDI_INPUT      = 0x800; //!< VST Plugin wants MIDI input
+const unsigned int PLUGIN_CAN_PROCESS_REPLACING = 0x1000; //!< VST Plugin cas use processReplacing()
+const unsigned int PLUGIN_HAS_COCKOS_EXTENSIONS = 0x2000; //!< VST Plugin has Cockos extensions
+const unsigned int PLUGIN_USES_OLD_VSTSDK       = 0x4000; //!< VST Plugin uses an old VST SDK
+const unsigned int PLUGIN_WANTS_MIDI_INPUT      = 0x8000; //!< VST Plugin wants MIDI input
 /**@}*/
 
 class VstPlugin : public CarlaPlugin
@@ -687,7 +687,7 @@ public:
         param.count = params;
 
         // plugin checks
-        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE);
+        m_hints &= ~(PLUGIN_IS_SYNTH | PLUGIN_USES_CHUNKS | PLUGIN_CAN_DRYWET | PLUGIN_CAN_VOLUME | PLUGIN_CAN_BALANCE | PLUGIN_CAN_FORCE_STEREO);
 
         intptr_t vstCategory = effect->dispatcher(effect, effGetPlugCategory, 0, 0, nullptr, 0.0f);
 
@@ -706,6 +706,9 @@ public:
         if (aOuts >= 2 && aOuts%2 == 0)
             m_hints |= PLUGIN_CAN_BALANCE;
 
+        if ((aIns == 0 || aIns == 2) && (aOuts == 0 || aOuts == 2))
+            m_hints |= PLUGIN_CAN_FORCE_STEREO;
+
         reloadPrograms(true);
 
         x_client->activate();
@@ -2302,13 +2305,7 @@ CarlaPlugin* CarlaPlugin::newVST(const initializer& init)
 #ifndef BUILD_BRIDGE
     if (carlaOptions.processMode == PROCESS_MODE_CONTINUOUS_RACK)
     {
-        const uint32_t ins  = plugin->audioInCount();
-        const uint32_t outs = plugin->audioOutCount();
-
-        const bool stereoInput = ins == 0 || ins == 2;
-        const bool stereoOutput = outs == 0 || outs == 2;
-
-        if (! (stereoInput && stereoOutput))
+        if (! plugin->hints() & PLUGIN_CAN_FORCE_STEREO)
         {
             setLastError("Carla's rack mode can only work with Stereo VST plugins, sorry!");
             delete plugin;
diff --git a/src/shared_carla.py b/src/shared_carla.py
index d98f808..ba5ddfe 100644
--- a/src/shared_carla.py
+++ b/src/shared_carla.py
@@ -59,14 +59,15 @@ MAX_PLUGINS    = 99
 MAX_PARAMETERS = 200
 
 # plugin hints
-PLUGIN_IS_BRIDGE          = 0x01
-PLUGIN_IS_SYNTH           = 0x02
-PLUGIN_HAS_GUI            = 0x04
-PLUGIN_USES_CHUNKS        = 0x08
-PLUGIN_USES_SINGLE_THREAD = 0x10
-PLUGIN_CAN_DRYWET         = 0x20
-PLUGIN_CAN_VOLUME         = 0x40
-PLUGIN_CAN_BALANCE        = 0x80
+PLUGIN_IS_BRIDGE          = 0x001
+PLUGIN_IS_SYNTH           = 0x002
+PLUGIN_HAS_GUI            = 0x004
+PLUGIN_USES_CHUNKS        = 0x008
+PLUGIN_USES_SINGLE_THREAD = 0x010
+PLUGIN_CAN_DRYWET         = 0x020
+PLUGIN_CAN_VOLUME         = 0x040
+PLUGIN_CAN_BALANCE        = 0x080
+PLUGIN_CAN_FORCE_STEREO   = 0x100
 
 # parameter hints
 PARAMETER_IS_BOOLEAN       = 0x01