Well, the attachment points are still in sheetmetal... even if you plate them on the inside (challenging, as the bedsides are double-walled, right?) it's still a bit scary, as all the weight is pushing in the direction of shear. At that point you may as well go full exo.
I'd rather put the weight on the roof, as the weight is the pushing against the plates ... I'd still do plates inside and out, to spread the force around, but at least the weight is NOT in the same direction as the shear, ya know?
Me, I don't have this issue ... I have no roof

... I keep thinking of a roof rack for the cage, but I'd rather store stuff down lower, keep my COG somewhat low. Okay, less high =)) ... 'swhy I took my spare off the cage, for instance.
-- A