I stumbled upon a minor, but nice improvement to the center key mechanism of the finger clusters. The current design is a square peg in a square hole, with a small amount of clearance all around. 

This is fine-ish, but the key post always needed a little bit of clean-up after printing so it can slide in the corresponding hole without binding. There's usually a bit of unevenness around the corners, and especially where the seam is, which can cause the key to rub and bind.

While working on switching over to an actual fabbed pcb, I had rounded the corners of the key post, so the corners wouldn't hit the radiused corners in the milled hole of the pcb.

After I printed some test pieces, I realized that this had an unexpected side-benefit - there's extra clearance between the rounded corner of the post and the still-square corner of the hole. And if the slicer places the seam on the rounded corner, the little "bump" from the seam no longer causes any issues, since there's extra clearance there in the corner. So the center key was able to move nicely in the cluster in an "as-printed" state, without having to add extra clearance (which would also increase undesirable lateral key wobble)