Had the same issue... With our Roadtrek 'B' I carried an inflatable canoe on a Hitch haul rack for many thousand miles. Not the performance of my hard shell boats, but got us out on the water. Moved to the 'B+', started looking at options, including those nice Yakima/Malone/Thule kayak trailers. Figured out it was CHEAPER and more versatile to set up the Suby as a toad, so now hard shells ride on roof rack on the Suby just like at home, plus I can get to launch areas much easier. My concern regarding the roof of the camper option, besides getting a tandem kayak up that high, was wind load while travelling on the camper frame - since it wasn't really designed for that. MPG loss while pulling the toad is maybe 1 to 1.5 mpg, with no change whether kayak is on it or not. Imagine I would have seen at least that with it on the roof, in addition to the structural concern. ST