Hey man, I misunderstood your message about the double shackle setup. With that setup you dont have to weld on new rear hangers, but I did end up welding new rear hangers because of my shackle angle.
Reason being is that with the stock location of the stock hanger, the shackle angle made for a rough ride. I moved the rear hanger forward about 3" to relax the second shackle thus providing a smoother ride. Again you don't have to weld on new hangers if you don't mind the ride quality, and the shackle angle.