Jubal, you are experienced in electrical systems and I know you did some wire upgrades for thicker gauge, have you tried this?
When I installed the PM4-45 MBA converter the only wiring change I made was using a 8 guage wire (was 10 ga) to connect the 12 V ground out of the WYCO distribution unit to the ground junction to equal the 8 guage 12 V battery positive wire that connects the WYCO unit to the batteries.
The adantages of the PM4-45 MBA converter :
It does not hesitate to transition to the bulk charge rate on demand. Better for generator use.
It is a four stage charger. PM4B models now includes built-in desulfation cycle to prevent stratification that can lead to battery sulfation.
I also made the change so I could use the PM4-45 MBA to maintain the batteries rather than
buy a seperate exterior charger.