Dave,
It's funny you should ask. I've been thinking of doing that with a camper that I imported from Australia. It's made by 3 Dog Camping, and my H-20 fits over the top of it perfectly. It would be a great way to have a comfortable lightweight camping setup and still carry the boat.
My camper is about 12-feet long and 7-feet wide. It pops open to a 12-foot by 20-foot tent with a queen size bed, kitchen and tons of storage for all of my camping and sailing gear. I'm sure the weight of the boat is a non-issue (the camper has trailer breaks), the trick is to mount hull cradles so they don't interfere with the operation of the camper and extend the tounge so the hulls don't pierce the back of the car in tight turns. You can check out a picture of the camper at
www.3dogcamping.com