The nRF52 based radio BT/Thread sub-board is so tiny and simple, it feels silly (and expensive) to fab it on its own. Should really melt it into the main board. But hey, it's the first time I've messed with RF traces/antennas, and the layout is a little tricky. Guess I'll just make a bunch of them as it'll be a handy board for a bunch of other things, too.