I am using some right angle male and female connectors to interface each of the modules. When the headers are at least 150mils (3.80mm) from the edge of the board, they "self-align" with the surface of the PCB. Unfortunately the connector to the Clock Generator Module on the PC-IR Module, was only 75mils from the edge, so it would not self align to the PCB. I went ahead and soldered the matching connector on the Clock Generator Module, and used my Hackaday Stick-Vise to align the two PCBs and soldered the header in place. This has been added to the "fix list" for revision B!