Applying lessons learned from 3b, I've sent off rev 3c to have four more PCBs made. If I don't find any serious problems, the next step will be to make 20 of these PCBs and have the PCB manufacturer also assemble them as a trial run for the final product. A looong time ago, I asked who would be interested in one of these 20 prototypes and I still have everyone's name who expressed interest. It's been a long road but the end is in sight.
In the meantime, I am going to work on PR-7820 support next.