The new and improved backpack PCB arrived. Better late than never I guess. I started by soldering on some headers.

I soldered a couple of female straight headers to hold the ESP-32, a couple of male pins to connect to the +5V and GND on the ESP, and a 90 degree Female header to attach the backpack to the CHESSmate PCB. In the rightmost image I have mounted the ESP-32 onto the board.

With the backpack ready I attached the stack comprised of the:

1. Membrane
2. 3D printed standoff with cutouts for the displays, LEDs, and buttons
3. CHESSmate PCB 

to the case with eight M3 x 14mm bolts.

Then I mounted the backpack CPU.

Once it was in place I connected the micro USB connector power leads to the backpack PCB and mounted the piezo speaker to the case with two sided tape.  

Popped the bottom of the case on, applied power, and viola a working CHESSmate reproduction.