I have a 2007 nnbs 1/2 ton that I installed a rough country 3"lift. I tow a 26 foot toyhauler. Before the lift the truck would sit level with the trailer hooked up. Now with the front end higher it squats in the back. I was looking at helwigs progressive spring kits either this one http://www.hellwigproducts.com/products/load-control/ez-990/ or this one http://www.hellwigproducts.com/products/load-control/pro-series/ . I also noticed they have bolt in air bag kits. Anyone have any pro and cons on either? Thanks in advance.