The brackets for my rear bumper eff...no play in my rear-mounted tire carrier:





The brackets push forward to contact the internal bracing inside the frame and into the boxed section. They are a very snug fit inside the frame and even w/o the side bolts, you can jack the rear end of the truck off the ground with the brackets sitting inside the frame rails. There is still about 1/2" of upward flex in the frame with the rear of the vehicle supported by the bumper.

I used to run a Smitty-clone tube bumper in back and every time I used it with the HiLift, I had to push it back down level since it's brackets were a very loose fit inside the frame.