I tow 25 ft 6000 lbs travel trailer with my 22 Silverado. By the way, the 4 cyl turbo w/8 speed does awesome (better than my old 4.8 V8 w/ 4 speed). Everything is within spec numbers wise. I am getting major rear end squat (generator and bikes ride in pickup bed). This is despite a properly tuned weight distribution hitch. When fully decked out I am still in the clear on payload/axle rating/gvwr/gcwr. I was considering heavier duty springs for the rear end, but then stumbled upon Sumo Springs. Anyone have any experience with them? The concept seems ideal for me since I tow only a few times per year.