. The air force knows all about structural integrity. may be they even beefed your bus up left and right for it to pass mil spec?
For mine being aluminum it is all about profiles and design to get the best strength out of the weight.
Accidents are hard to model and repeat. But I have rather two layers of metal in a roll over then one.
I agree on the tin can effect, may be some wall carpets can help.
If I ever decide to improve on insulation and strength I will be taking the inner skin of , removing old insulation, get 2 component polyurethane insulation kit and put the inner metal sheet back in with an added nylon washer between the sheet and the framing ( cold bridge ) . With every set of fasteners I would spray a layer of foam in between so that everything bonds together.