Finally got the circuit boards from OSHPark!
After verifying that there were no shorts, I installed the shield pins. Good tip when assembling a shield: put the header pins into the Arduino first, then solder the pins to the shield PCB. With the shield installed on the Arduino, I verified that 5V was getting everywhere it was supposed to. I then proceeded to assemble the first shift register circuit (U1 + 8x10K resistors).
Testing was a success - using a jumper cable I bridged pin 1-8 to ground and got the expected MIDI notes on the computer. Next step was to install the second shift register (U2) , which is daisy chained to the first register (U1). Again this worked as expected.
After completing the shield assembly, the hardware & software part is complete!
Now comes the mechanical part, figuring out a way to install 32 reed switches & magnets to the pedalboard. I have been testing various magnets to determine at what distance the magnet closes the switch, as I need this to be a good 10-15mm in order to deal with the travel on the pedals. Details to follow!