I know this is an old thread, but I did exactly what the OP was trying to do:
1. Dual Odyssey PC1500 Group 34M
2. Genesis dual battery
3. Noco Genius GenM2 onboard charge controller
4. AC inlet on driver-side fender.
I then made a custom bracket, installed a few remote DC circuits (MRBF...
Any chance you are interested in an IP68-rated onboard charger? If so, you might want to consider the Noco Gen2, which is a two-bank charger with 10A per bank and rated to charge two 230Ah batteries. Yes, it's a bit light for a 200+ Ah battery, but the IP rating and onboard install might be...