" Mounting stuff on top of the camper " ???
My advise is : DON'T
My only experience is with a Hawk with the extended bed, maybe other models are different. I could lift and lower the roof with a solar panel and an empty roof rack, but that's it. If you load anything on the roof rack, you will probably have to unload it every time you want to raise or lower the roof. At the very least try before you buy. These racks are expensive, don't invest in one only to find it does not work for your needs. I built a seperate roof rack to carry heavy gear and only left one Yakima bar on the camper roof to act as a brush guard for the fragile plastic vent and solar panel.
Cheers
Mark