So the boards showed up (it seems they were riding around town in the back of a delivery truck for a few days). I soldered one, which resulted in a mostly working board :) A few issues:

- the 5V boost vented Magic Smoke when first powered. Used 22 pF instead of 22 uF on the main output (ooops!) I bypassed the boost, and the 3.7V power seemed fine for the whole board!

- The SRAM is really 128KB, and I left A16 floating. Shorted that to the adjacent pin (A14) and the SRAM stabilized. I'll ground it in the next version, maybe farm it out to an edge connector later for rapidd context switch :)

- The register I'm using for latching user output (OUT opcode) has an active-low CLEAR input. I tied that to ground by mistake, so user output was always 0. I wired it to a nearby 5V+resistor point, and that works fine now.