If your springs a set up properly, the body will seperate from the axle, or rise, and snubber and/or slappers are rendered useless.

Slappers typically hit the leafs just aft of the main eye, right in the weakest part of the spring. If the are doing that, good chance your going to bend your main leaf as it trys to lever the car's body up. Think of it this way, would you use a floor jack in this spot? That's what slappers are doing.