There is just something about carrying a large can of fuel (gasoline or propane) inside that doesn't settle with me. I'd think you'd be able to make some kind of box sized to the generator and a fuel can for the rear bumper. If you have a walk thru, a receiver could be mounted off to one side. A heavy duty bearing mount could even be incorporated to swing the box if its necessary. Pull it off at home. Also I've seen members who use a receiver mounted hitch box on the front.
Donmc is the one with the sheetmetal/vented cabinet for his Honda 2000.