I transported 2 Wilderness System Sea Kayaks on the roof of my Class C.
I was hesitant to install anchors and came up with a method that worked.
I made a set of 4 cradles using Styrofoam panels and canned insulation foam. They were sturdy enough to support the kayaks. I actually embedded rope in each to be able to secure the kayaks. I also made a spacer to keep them separated.
In the front I would run straps down the side of the motorhome and used the foam blocks used to transport a canoe on a vehicle roof, the blocks held the straps off the top corners of the Class C room. I installed a solid anchor at the bottom of the side directly below the front strap location.
In the rear I secured one side of the kayak to the roof ladder, this kept the kayaks from moving side to side. I also ran a strap down the back and tied it off to the trailer hitch.
I transported the kayaks from TN to FL, Maine, Wisconsin without a problem.
That being said I never considered trying it our current coach but strap them to the roof of the Jeep I tow.
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi