Nice to see someone is going to try this! I am currently on holiday (on Budapest airport wifi right now, transiting Prague-St Petersburg) and back in October so can help you out in earnest then.
I take it you mean an Uno? I'm not aware of an Arduino Duo.
In related matters, I've drawn up a schematic and PCB in KiCad and will be sending it off for manufacturing in October. I'll put the design files on the webpage then too, and make the spare PCBs (if error-free) from the prototype run available.
I've also added (due to request from an lfpf-er) a rotary encoder for exposure changes. It's completely optional in the build though; just leave it out if you don't want it.