Last week I ran across a bolt on hitch receiver at a local hardware store (Princess Auto for the Canadians out there) and the same day I bought a four bike carrier I found on Kijiji. I also had to get the reducer for the receiver to go from 2" down to the 1 1/8" bike rack tongue.

I mounted it on top of the bumper as opposed to underneath to give me a bit better clearance out back - didn't want to risk the bikes backing into or leaving certain campsites. The rack can quickly be either fold down or be removed to enable the end bunk to fold down. The spare tire mount had to be slid to the side as well but no so far as to interfere with the support for the bunk.

And yes I know there are plenty of folks out there who don't like the idea of having anything attached to the bumper.......