are you planning on running semi wheels? on the dually in the avatar?? maybe able to get away with 10" i have a very high offset on my wheels with maybe 2 inches of backspacing plus the adaptors and a icon 11" lift, i have had to trim bumper and fender to clear it! should have ran the 4.5" hangers instead of the 3" ones on my truck now with 8" springs and would have been about right....