The unknown pair of pins next to “M1 A0” in the “9x2 Header strip” are both GND, available for whatever you want as you surmised.
The unknown pair of pins next to “Power interconnect” in the “9x2 Header strip” are both +5V (from Arduino), available for whatever you want as you surmised.
The middle pin of all the Servo headers is +5V (from Arduino).
The top pin of all the Servo headers connect to an Arduino PWM pin corresponding to the speed control for the various motor channels. The associated motor channels are labeled on the PCB under the headers (left to right: M3, M5, M4, M2, M1, M6). The corresponding Digital pins on the Arduino are correspondingly labelled for ease of reference (noting that M1 and M6 are select-able by way of the first two columns of the 3x5 header J1; where wM1 and wM6 correspond to J1 column 1 in the “up” position and J1 column 2 in the “up” position respectively).
By the way, thanks for doing this. I’ll include a link your docs to our README if you’d permit me, and when you think that would be useful to do.
