You know Ewarnerusa, you just gave me an idea.
My TT has the front kitchen and the factory solar wiring comes right out of the bottom of the front wall because the batteries are right on the other side of the front wall sitting 4" away on the tongue.
What I can do is drill a hole down from one of the base cabinets through the floor, pull the factory wiring up into the cabinet, install the controller in the cabinet and run 2' of new wire back out to the batteries. That makes it lot easier than running new wiring down from the roof and puts the controller inside.
While studying this idea I'll wait a week to see if only comes up with a waterproof controller.
As for four batteries, you're right, I probably don't need them though I'm retired and do spend more than weekends out. I think it's just that I'm used to four of them in my MH? And I found a neat way to add the other two with a little bit of welding.
Bill