i used to have a twin pipe backbox and for the life of me i couldnt get it to sit right, one side always flopped down that tiny bit and it annoyed me soo much, but that was just a backbox, what i have now is a custom catback with two hangers(OEM + custom made one that attaches to the bumper bracket) and it sits perfect i think. just watch it doesnt sit too close to the bumper/touch it because it will cause the bumper to rattle which was annoying!