I pondered my wiring diagram for a while, then settled on a new arrangement for the PCB and spent the next 5 hours re-making it. I've interrupted one aft stick circuit with a connector to the TRIM switch and the other five stick functions with Double Pole Double Throw (DPDT) relays powered off the OTHERS switch. I have a spare relay pole (blue wires) that could be used if a channel were to fail in future. There are three independent tracks for each stick grip - two for each comm and one for each 'flap up' wire (per the TCW Intelligent Flap Controller diagram). Next I'll solder on the wire terminals and determine which holes each of the stick grip functions ought to be placed ... that's brain teaser in itself. The output sides come to a common connector to run out to the devices.