I can't pan my Clavinova clp-555 which is my slave and piano. For some reason it won't accept that midi control. Is my option to either record it to audio or find another piano sound (my Proteus 2000 piano patches suck). It's a livingroom consumer product.
Sometimes devices support panning through sysex. (YAMAHA TG55 does for example). If so, you can program Metro's pan knobs. Check the back of your manual if so inclined.