I agree with nvshooter, its slapping your internal stop witch may make it louder than with moleskin and shelf contact.
This is all i did to mine, it sems very quiet this way. Its just a small section of camo stickyback felt on the shelf and i did the whole backside of the launcher with the same felt. and i agree, loose the football and serve it into the cable.
oops, forgot the pic here it is!