I want to point out that the reason for questioning the strength is not as obvious as it would seem. I have some other ideas for the camper shell and I wanted to get a general impression from the crew here of its need to have a roof clamp down to keep the sides from undoing themselves while in motion..
I hope to visit the builders before the the end of March.
One of the frustrations you'll see expressed here from many FWC owners it the lack of documentation on where exactly those aluminum channels are located under the skin. FWC refuses to say where exactly they are placed, claiming there are no specific fabrication drawings and they are simply welded together by eye. (As a former engineer I could not fathom how/why they'd do it that way, but there it is.)
Makes it extremely difficult if you want to mount anything to the outside later, such as gas can, traction ramps, etc. I "solved" the problem by mounting my MaxTrax using homebuilt brackets attached to the aluminum skin using 3M commercial grade double-sided tape (not the consumer stuff you find at Home Depot.) I did the same when I mounted a solar panel to the roof. Haven't had any problems with either installation.
So, if you want to mount something later, I'd suggest getting them to install a general purpose bracket at the time of assembly (assuming they'll agree to that.)