My fear would be that sure is along way behind you using the rear bumper/ladder area of a fifth wheel.. You are sort of at the mercy of flashing lights and finger pointing from passing cars haha... I've pulled up behind alot of fifth wheel trailers with things swinging in the wind mounted to the rear area. This has got to be the worse place possible vibration wise for mounting things... The driver has no idea what is going on back there...
The advantage of the travel trailer style at least you can store thing on the front of the trailer where you can keep some sort of eyes on it...
A rack over the truck cab and extending out over the truck hood might be good idea as well. Like some of the kayaks that are being transported with fifth wheel hookups.
You certainly see most everyone just loading up the hallway or the couch areas in the fifth wheel trailers with their larger items to transport... I even saw one guy load his two kayaks inside the fifth wheel once. Guess he had a rack over the couch or something like that...
The fifth wheel toy haulers sure would help out this situation big time...
Roy Ken