My 96 Yukon sags pretty bad in the back, several inches lower than the front. I generally have 2-400 lbs of tools and materials in the back, but even without that its still noticeably lower. I need to tow a trailer (few thousand lb total) semi-regularly, and the rear will bottom out if I hook the trailer up I think the springs are shot, and I want to replace them with something beefier than stock. Has anyone used the heavy duty springs from General Spring, or have another recommendation? I'm mainly wondering if/how they will affect the ride quality. A little stiffer I wouldn't mind, but I drive this thing every day so I want to avoid the covered wagon experience.