I received some of the parts I need for developing the prototype of the PEU. I have the display, the key buttons and a proto pcb. I've soldered these parts together and here's a picture.
For the prototype, I'll probably use a separate board of the same type to mount the Teensy 3.6 main processor and the code module. In a final design, I'm planning on laying out a PCB using mostly surface-mount parts with the Teensy 3.6 and code module mounting on the back-side behind the display.