Give Feedback on initial House Batt charging upgrade plan

If all you are trying to do is get more voltage (and current) to the house batteries, from the engine alternator when driving, you should forget those fancy isolators and install a simple switch controlled continuous duty solenoid between the chassis and house batteries.

About $24 for the solenoid and maybe $10 worth of cables.

You probably already have a solenoid installed for your aux/emrg start function. Just add a toggle switch to parallel the aux start temporary contact switch.