Changed the outline a bunch, printed off sheets of paper to mock them up, and then finalised the design.
The available area was much smaller than I originally assumed. It doesn't really have room for the PIC18F14K50 that I was planning on using. That's okay! I have a pile of them, but there are better suited PIC families that are cheap, too.
Although these are much more attractive in @oshpark purple, obviously.
So they're ordered, because I laser cut them out and fit-tested them, and I think they'll work great. They cost $3.95 for three. Ordered in 0.8mm FR4, because I need all the height I can get.