Thanks. One thing I opted to do was install a small 2x3" 16 gauge steel backing plate between the body and the nut on the bottom. It's more reinforcing than the factory used and if you were in a really bad accident it would help prevent the nut and washer from pulling through the floor.
I need to hit the entire wheelwells with undercoat now...judicious use of the high pressure nozzle in the wheelwells after trips has really thinned the factory stuff.