The weak point can be seen very easily here: Bumber is too short to reach up to rear bracket. So there's only thin aluminum tunnel between them and that will not hold up nothing.
That is fix is good idea but will not prevent braking it again (unless you have uninstalled rear brackets and the steel plate goes all the way below bracket? Still you need to rivet bumper and steel plate together - IMHO). The strongest parts in the tunnel are that aluminum tube (bumber) and rear bracket so they need to be mounted together TIGHT. After that it will work ok. I'm thinking some extra steel support between those two parts.
My current setup is longer rear bumper. I bought -09 bumper which is for 162". I cut it shorter a little but still long enough so I could rivet it into rear bracket (from inside the tunnel and below foot rest with 4 rivets). My sled is 141" so I needed to cut it a little. My pal has 153" sled and he did not cut 162" bumber at all in his conversion.
They are quite strong now, but still need some extra support - just to be safe. We have carried 10-20 liter extra gas in rear while driving/jumping and tunnels are still looking good
