On Friday the boards arrived. A quick test fit showed that all the contacts were properly aligned.
For some reason, the Type C receptacle on the first board I assembled went up in smoke after a wile. My computer didn't indicate a over current condition. Since the burnt spot was on the USB connector only and it seemed to have happened sporadically, I suspect that a rouge solder bubble might have been the cause.
My second attempt was more successful. Although I had double checked the schematic, I made the classic mistake of switching D+ and D- on the STM32. After some failed board surgery, I discovered that I can fix the problem by rearranging the resistors that are in series with the data lines.
I also wasn't patient enough to wait for the right parts to arrive. I desolderd the STM32 from a BluePill board and made some parts fit with wire.
After finding and fixing the mistakes over the weekend I successfully flashed the versaloon firmware onto the STM32.
The are three bodges and a lot of flux on the board, but USB enumerated and that's all that mattered.
Finally I confirmed that all is working by programming the pin-scan bitstream on the FPGA.