Hello ! First, I would like to congratulate you for this project.. That's just amazing and clever.
I just want to know if this controller can be used as a Command 8. Can we assign several faders to several zones on the soundplane ?
Although it would be up to the user to figure it out I think being able to define an area of the sound plane as a rotary encoder would be most slick.
If it should mainly be used for that, maybe just print it on the reverse of the polyethylene layer?
I guess one could also insert a sheet of paper with the layout; or a white one and have some kind of cheap projector over it; or should that make the soundplane's response considerably worse?
Since the Soundplane is a true force sensor, stickers and so forth on the surface don't hurt the response at all. If you wanted a big area you would have to add gaps to keep the surface flexible.