I'm getting a 6" lift, I want the best highway manners for my kids at the same time I want to be able to load up the back of my burb with gear and tow the boat without the back end sagging like crazy. I just saw a new expedition w/ a 4" lift towing a couple snowmobiles and the thing was sagging like a stink-bug. I dont want that. Any suggestions on any particular model springs that might suit me? Thanks.