Assembly notes:

For battery holders BT1, BT2, BT3 (NOT BT4!) break the rear walls off before soldering, so that a battery can pass all the way through the holder. Flush-cut everything on the top side as close as possible, and re-flow the cut posts to smooth them into domes. Optionally solder 2 short bits of wire from the two exposed vias to the rear walls of BT4 to mechanically strengthen those walls. Solder a 25mm piece of 0.6mm solid core insulated wire to the GND side of the big yellow capacitor on the REXCPM.

Qwiic adapter wire connections:

BLACK -> new GND pin on the large yellow cap

RED -> pin closest to the cap

BLUE -> center pin

YELLOW -> pin furthest away from the cap