5 mph bumpers: Replace with something different/older?

You may be able to secure them bumper shocks between a couple cinder blocks put a board over the bumper receptacle part and gently whack them with a sledge to bring them in. The shocks are from my experience not providing much impedance to compression. I vaguely remember drilling a hole in the rear of the shock to release the 9 trillion pounds of compressed hydrogen contained inside. Kidding.

I believe I did drill a little relief hole in the rear of the shock though. Safety goggles and gloves are always a good idea when playing with a sledge or a shock with gas in it. Now that I am older, and have almost blinded my self about 40 times, I like goggles.

Keep us posted on your bumpers!