I had that problem too. Bent the hangers and ended up with a really annoying rattle against the heat shield. Spent 2 weeks messing with bending the hangers, then I realized that the exhaust was just about 1/4" too long. When I unbolted it at the flange right behind the resonator the rear section would hang PERFECT but in order to get it back together I almost had to wedge it in. I ended up taking it to an exhaust shop and having them remove that flange and weld in a coupling. No more rattles or burnt rear bumper for me. Oh and I didn't have any problems with the Kartboy hangers moving around, it was a b**** getting them on and they fit so tight I can't imagine them moving.
Good Luck!