I try to center them between the jounce and rebound bumpers. If you lower it too close to the bumper, it can put a bind on the control arm travel, it will ride like crap and you just might break something. Years ago, I bought a repo Dustpan. The PO was a huge fan of the snow plow look. It was riding on the lower control arm bumpers, and had cracked the upper control arm frame ears, among other damage.