Disabling the centre speaker

I’ve recently got a Match DSP set up. It works moderately well, eq’d using a UMIK1. 
 

The issue I’m having is that I can’t disable audio via the centre channel. One option would be just unplugging it, but it handles nav, phone and warning noises. 
 

As far as I can tell, it’s handled by the SOS unit, however signal must get from the HU to the SOS. 
 

Is there any graceful way to disable? What have others done when adding aftermarket audio?

It seems the VW units have a lot more options re external processors in long coding. AFAICS the Skoda only has MOST enablement (presumably for canton). Is there anything I’m missing?