If i were going to use 6 v. batteries i would have a small grp 24 , 12 volt on the side . Just in case one battery goes bad while on a trip, you can still have 12 v. power to run things.
This works for me in my situation because i fish using a trolling motor, therefore, i carry a 12 v. battery anyway.
If you plan to use it with water while its off the truck, i would support the bottom.
The main camper ground has a tendency to rust on many AF units. My 860 had a common ground hidden between the water heater and the front drivers side firewall,held by a screw into the camper frame. Its impossible to get at it unless you are a trained mechanical hamster with a miniature tool kit.
When my ground finally stopped grounding and left me with no power,i had no choice but to hook up the generator ground wire in the genny compartment. ( i did not have an on-board genny at the time, just the empty compartment that was pre-wired) Using that ground wire, grounded my 860. I used it and left it that way for the rest of its life with me.
Best of luck with your new to you 860, enjoy ,
Bob