This is what did to a stock fiddy frame I from BBR for a $100. That is a 1/4" x 1" steel plate cut to the same arch as the frame welded in there. It stops just before where the engine would sit. I had to remove the stock air filter mount for clearance. After reading some of your post I should have braced the sub-frame too, But I didn`t bend the last one so I`ll see what happens. I have been giving it the torture test on my back yard double and there has been no signs of it bending. Now if I could only do something about my sore ankles and wrist.