Few years ago, i enclosed the hitch area with two 20 lb propane tanks inside plus the standard battery.
It worked really well but I had to put a side-mounted jack on the frame because of the crank handle.
A keen fan of dry camping, I decided I needed a back-up sewage tank so purchased a Thetford tank.
The problem has been where to stow it. The back canopy area of my 1500 Ram has drawers under a false floor, so leaks or spills would be disastrous.
I finally decided to build a higher compartment and stow the tank vertically agains the Pod front wall. I finished building it in the Fall and it seems to be OK. We shall see on the long haul to Arizona in January.
A side door give access to a 30 lb propane tank and the sewage tank goes in rather tightly. There is storage now for two batteries, so added to the solar system atop my truck, we shall have lots of power.
I forgot to get pictures (Duh) of the finished product, but will get some next time I visit storage.