Thanks. Actually, I put a 45 degree “chamfer” on the corners of the grooves. When you’re sliding it helps the fingers slide across, and when you’re looking to lock into a groove they help center your finger. So I think it addresses the finger pain problem you mention.
Unfortunately on this last batch I think I caused a lot of grief since my unit worked but a few recipients had trouble. I think what happened is that if the boundary is too thin then the edge sensor contacts don’t get properly engaged and various columns don’t function properly. That discouraged me but I think I need to get back in the saddle and do another iteration.