Ha anybody installed them on their van and how did/do you like them? I'd like to stiffen up the rear of my van a little. When I hit a dip or a bump the back slams down. I don't want air shocks. I put them in my Dad's wagon and I don't like the ride. I don't want air bags because of the cost and the time to install or do the fabrication. I heard a helper-leaf will make it too stiff. I need some opinions.