I'm using an existing project that already wrote an debugged all the code, which is why I went with the nano. After my janky little prototype worked, I designed a hat for this. I'm going to have a buddy review it next. If I get the 👍, I'll order 3 boards & the components, build out one board, possibly repeat this process a few more times, to get a working setup, and submit a merge request to get the KiCAD files upstreamed.

It'll be a while before it's done, but it'll be a good experience to build my first hat (for anything!) 

 Right on. Where you ordering pcbs feom these days?  

 For prototyping, OSH Park.

For production runs, it depends on the size of the board. I'll stick with OSH Park if it's a small board, but they're way too expensive for anything bigger than a couple inches. For those I usually go to jlcpcb, but I've also ordered from pcbgogo and a couple others.