While waiting for the PCBs (they might not make it in time after all, I'm afraid), I'm still working on the faceplates. In order to correctly place all the holes for the CPX's LEDs and sensors, I prepared an image of the PCB with the CPX overlaid on top of it (lifted from Adafruit's Fritzing library):

Then I printed that on normal paper, and used a knife to cut out all the places where there is something that needs to be exposed. Then just align it with the outline of the faceplate, and gently shade the whole thing with a pencil:

The last step is just a scrollsaw and a dremel tool. You can also see on this photo the cool purple bolt nuts that I found, to be used to secure the CPX to the board.