It’s possible to assign PitchBend, Aftertouch, ModWheel and CC74 in mod matrix. So you adjust these to your liking, reduce the voice allocation to 1, then save the patch and load it to remaining 3 Instruments which respond to different MIDI channels and you have a 4 voice MPE Combo. It works nicely with Linnstrument which AFAIK is more flexible than Seaboard configuration-wise. I’m using ModWheel on Y-axis instead of MPEs default CC74 since most of the hardware synths and their patches already have interesting modulations bound to it.