If you towed a car that is the place for a canoe or kayak. But we don't. So our canoe or kayaks, go on top of the RV on a simple to make and install galvanized 3/4" pipe racks, attached to floor flanges bolted to the roof.
The canoe sits on the back rack and 2 pipe racks. I put a plastic pipe on the back rack that acts as a roller.
Here is a rack I put on an old 23' Class A. Same method.
People worry about holes in the roof, You already have plenty, they seal up nicely with roof sealant.
Locate the floor flanges so at least 2 bolts hit the aluminum roof joists. They are easy to locate. On a cool morning, climb up there and the condensation on the roof shows where the joists are located.
I have never had a leak. I hit one with a tree branch once and it pulled loose. I just reattached it and sealed it again.