I've eliminated damage to my front arms by building a custom Kydex bumper:







If you don't want to make one yourself... I'll sell one for $15 shipped in the US, you need to cut 3mm off the posts of the upper deck support, then use longer M3x20mm screws to fasten the Kydex bumper. Usually the Kydex bends with hard hits, and I can bend it back, I've yet to break an arm or upright with the bumper yet, but I have damaged the lower bumper mount once from a really hard crash into a disabled car on the track once. I've been racing with a 21.5T motor in the USGT class.