Have finished designing a new PCB, the fifth iteration since I started the project. I'm waiting for it to arrive from China, but here's roughly what it will look like:
The overall footprint is a little longer to make room for the MIDI ports, there's more info included on the silkscreen layer, there's an extra LED to show when the power is on, the volume and power controls are now aligned with the audio output, and there are a bunch of boring changes to the component layout on the other side. Oh, and everything is red now.
I've also ordered some black nylon knurled thumbscrews to allow the batteries to be changed without needing a screwdriver.
Meanwhile, coding continues, and I've sent a V4 prototype to Pasadena for Supercon. I won't be there, but hopefully DrumKid will!