Dale Ruptash, I had this same problem this year at Snowbirds. I went through about 4 bumpers in 2 days....and I really didn't hit anything
What I did was run longer screws. I know this sounds simple but this is what I did and I didn't have a problem from that point forward. On the 3 parts that hold the bumper (2 plastic molds) together run the longest screw that will fit. It's important that the screws run "ALL" the way through the bumper. This will put more stress on the screw and not the plastic.