After a long discussion with Emagair's Brad Dement, I decided to simplify the PMag wiring and just use the Klixon breakers to kill power for testing. I also replaced the switch that was intended to control a MAP air valve with just a curve A/curve B switch connected to the PMag serial lines.
I am also planning on putting connectors on the panel for the L & R PMag serial ports. I'll use the EICAD software on my laptop for PMag configuration and timing customization, connected to these ports. The ports will be on a 2" blank, occupying one of the MFD instrument positions. Eventually, I will develop a complete controller using a huVVer-AVI instrument to replace the external laptop.