If back bumpers are so fragile while are so many spare tires mounted there?
I have a tandem that I 've carried on the back of three of my last four RV's. The spare rides in the back of the truck. The bike weighs a little more than the spare but not much. I guess I could be flirting with disaster, but it doesn't seem much different than a spare to me.
My bike rack consists of 2 tubular receptacles on each side of the bumper. The wheels of the bike sit in the receptacles.