boy would you see a disappearing act by the salesman. really though, this is a stress crack. thats all. as a former service manager, i have seen this in trailers, 5th wheels, and all kind of rv's..
if its stated on the original factory warranty, as structural damage, the mfg will look at it says you took it off road, and its not covered. especially because of the age.
the dealer will give him an estimate for the repair. the insurance company will deny it calling it structural damage..
so it falls to the owner to repair it. a small strip to cover the crack would suffice for me, especially because of the cost.