Eric,

I've transported a Hobie 18 on a van roof rack made for catamarans...just need a lot of TALL guys to put it on and off <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" /> The rack I used had rollers on the back (similar to a boat trailer) to help in loading and unloading the beast. It also had clearence lights on the ends due to the width. I've also seen boats on top of RV's and travel trailers. The best way to position your boat on the rack is right-side up, bows forward. This makes loading and unloading easier. No worries about the mast overhang. You just need to red flag the end if it extends 6 feet past the rear support (CA law?). Neccessity is the mother of invention. You'll be OK. Just make sure the rack is securely fastened to the van and that the boat is tied down good.

Your gas mileage will suck.

Safe travels.