check out this link viewtopic.php?f=11&t=1262&hilit=+rack
It's a deck I made for my bus, it's as wide as the bus and about 5 feet long. It's very strong and works well.. However it's very heavy (at least 300lbs) and a huge pain in the ass to put on and take off the bus... I need at least 3 people to do it. It's also very high off the ground which makes it hard to load anything on it. I do have a hill in my yard that I can back up to
and load things like motorcycles on it.
I think you're time and money are better spent getting a trailer hitch.. at least for my needs.