Recently got the expression & crescendo pedals installed. The pedals were salvaged from an old organ and tension is adjusted with a wing nut - very crude but effective.
The pedals use a 10k ohm long travel sliding potentiometer to register the pedal position. I designed a dual-purpose PCB which mounts the potentiometer and also attaches to the slider. I made 3D printed brackets in Fusion360 to mount the potentiometer. I will have to change to a shorter travel potentiometer, are these were hard to position and will be vulnerable to damage. The design will be changed to use a 3D printed enclosure for added durability. For now it serves the purpose. The taped wood block is a temporary pedal travel limiter - something else to consider for version 2.
And here are the pedals installed somewhat temporarily positioned according to the AGO console specifications. This will be a useful template when we get around to building the final console. Have yet to decide whether it'll be a wooden or (more likely) sliding/adjustable square steel tubing so it can be disassembled easily.
The Hauptwerk software detected the pedals immediately and just worked, which meant I got the Teensy software right the first time - that doesn't happen very often!