rpm are not metal they are basically a heavy duty plastic
I know I just mean its a bad idea in general for anyone to use all metal bumpers, braces and bulkheads, since the shock is transfered through them to more critical areas. RPM bumpers are super absorbant and rarely ever brake, so they are ideal for bashing & racing.
i shredded an RPM front bumper. head-on collision with a pole, and the pole won. a couple big chunks of RPM plastic went flying.
the only metal bumper w/metal supports that seems to make sense is VBS bumpers, ti VBS skids and ti jounces. the jounces act as a spring to absorb impact, and the titanium acts as a spring in itself (to a certain degree of impact. a lot will mess it up, i'm sure). i won't be testing it...