Mixed news.
The layout fits and I’m fairly happy with it. The lowest thumb keycaps needed a bit of trimming, but they’re comfortable.
The board works with QMK outside the reform, and I figured out serial code that should talk to the LPC and display battery voltage on the OLED using the same font as the stock firmware.
… And in the process of plugging it for final testing I broke something on the motherboard. Until I have a repair or replacement, I’ll have to put the keyboard project on hold.