Ducky's Dad
Explorer
I'm doing something similar on a Tundra CrewMax with a 5.5' bed, but I'm going with the Yakima tracks screwed through the top of the fiberglass shell and Yakima gutter mounts on the cab, so that I don't have to drill the sheet metal. I also have a Yakima DryDock that fits into the receiver hitch, and all components have 66" crossbars. This setup gives me four bearing points over a length of maybe twelve feet when necessary, and distributes the load over the shell, the cab, and the receiver hitch. I have the same tracks on my other truck shells and they have been real handy for everything from ladders and lumber to bass boats and decoys. One truck has a Con-Ferr basket mounted to the Yakima bars, and that basket/rail system is the base for an EZ-Awn Bat 270, an 18-gallon PVC water tank, four MaxTraxx, and whatever else won't fit inside the shell. Once you you are committed to a rack system like Yakima or Thule, it makes sense to stick with the system.