Rhino Lining may be alittle on the heavy side.( just a guess) but they do have products very similar.
Possibly a hard clear coat of a spray paint...
Possibly that new Garage floor paint ( is like rhino lining for your garage floor)

My thought was to make a mold of the chassis in clay or w/e then pour plastic into the mold...let set, and you have a cover for the bottom of your chassis. With that done you only have to deal with one or 2 striped screws rather than all of them.
Dunno, just ideas..