Looking at the tongue on your 2012 Keystone Sprinter 311BHS trailer shows just enough room it appears for ONE BATTERY deep to be mounted. If your propane door just unlatches and lifts straight out it probably clears the one battery height ok. It it hinges before lifting out it would have to clear the one battery but I think you can remove all four latches and get to the propane tanks ok.
If you have room for one battery mounted on top of the tongue using a a couple pieces of steel angle material you should be able to mount two or three batteries sitting side by side that would extend out over both sides of the tongue.
This is what I did with my OFF-ROAD POPUP and had four GP24 batteries sitting side by side here until one failed on me so then ended with the three you see in this photo. I just mounted them end to end sitting in one of those plastic battery cases. They were separate just enough to allow you to snap on the plastic battery case top...
maybe something like this would work in your situation???
My point here is the angle pieces will hold the three plastic battery cases end to end across the tongue. They will probably extend out one half length of a battery on each side since you are close to the start of the trailer tongue????
Roy Ken
