I know, the back bumper is not the place for a spare, IMO. Even if you cover the tire with an amusing, attractive cover, there is a good possibility that the cover will need replacing eventually. My spare is currently sitting in the shower stall. Of course, it will get moved when underway and I'm looking for a spare mounting solution.
They do make an under-trailer mount that hinges up between the frame rails and, in my case, will only subtract 2" or so to the clearance. I may mount the spare under the tongue, though, as any hazard will probably hit my differential or the hitch before it rips the spare off.
Subscribed to this to see what is offered up by other members.