I cut the rivets off my rear leafs, and slipped 3 extra leaves in between the stock leaves to lift the rear about 2 1/2". I'd used a metal cutoff saw to cut the leaves to length, looks like they were done at the factory. Bolted everything back together using a grade 8 1/2" bolt and Nylock nut (after opening the 7/16" holes up a bit), didn't have to mess with the pinion angle by using shims, either. Used longer u-bolts, and cut the excess thread off with my sawzall.
Noticeably more stability when going through turns (as the springs ARE stiffer), and I can carry a LOT more weight in the back. Have put over 1800lbs in the back, and not bottomed out. Yes, it rides like a truck, not a car, but I'm always carrying supplies and tools anyway.