Another option is a storage shelf attached to the hitch. For the R model, be sure not to block the slider or else tape off the slide switch until you remove the rack when parked.
I'm sure everyone has an opinion, but I wouldn't put one in an enclosed space, especially part of the MH. I won't even put my grill tank in the garage in the winter. Propane tanks stay outdoors, period.
Land of 10,000 Lakes
2016 Forester MBS 2401R
2016 Forester 2401R