This dense self-adhesive foam will absorb just about all the energy of a fast-moving ball and stop it dead in its tracks. Put it in a ball scoop to reduce damage and prevent bounce-out.
Sold in strips approximately 1" by 6". Cut to size, clean the metal with alcohol, and press it in place. Make sure that the foam does not interfere with the eject.
Medieval Madness - prevents the ball from bouncing out of the Merlin hole.