Follow-Up:
I got a VW Eurovan camper this summer and ran into the same problem with transporting sea kayaks. I ended up buying a MicroTrailer from SportsRig.com out of San Luis Obispo, CA. The trailer is a little expensive, but they use motorcycle wheels and shocks, rather than stiff leaf springs and small trailer wheels. The result is a soft smooth ride for lightweight boats - a perfect compliment to the small camper setup I have. The trailer also folds up and I store it up against a wall in my garage instead of subjecting it to the weather outside.