Hi Dave,
Sx piano definitely sounds better played via. p121.

It’s awesome. P121 sustain pedal works, ( I was going to have to buy a new one for the sx, my old one is playing up after 30 years, haha. Can’t complain.)

I can actually mute the piano part on sx and use p121 piano sound across the whole piano keyboard ( personally think p121 piano sounds better than sx piano, but that’s me.

Still deciding on stacking vs L shape setup.

Basically got myself a Clavinova of sorts. haha

Thank you Frans for finding this app. Inadvertently it was what I was looking for to get midi functions on my p121.