The plane was configured for a single battery. But you want to go to dual Electronic mags. I saw this on line. A dual battery isolator the allows both batteries to be charged by one alternator. Isolates the main start battery from the second. Has an emergency override ability in case the main/start battery dies. So you still have a backup battery for the P mags. Except for the emergency switch it is all wired at the battery. Seems like it would work well for our application with dual P Mags.
250 AMP Intelligent Dual Battery Isolator Universal 12V 24V VSR Voltage Sensitive Relay for Car, Truck, ATV, Emergency Battery Starter
250 AMP Intelligent Dual Battery Isolator Universal 12V 24V VSR Voltage Sensitive Relay for Car, Truck, ATV, Emergency Battery Starter