I recently had a pop bumper mounting hole stripped on my Monte Carlo EM. I considered Travish 's recommendation but the nut would have interfered with the pop's center mechanism. I wood-filled the hole, drilled a new pilot hole, and was good to go.
Quoted from Travish:Or if the backside is clear you can get a post that goes through the playfield and has a nut on the back
-Rob
-visit http://www.kahr.us to get my daughterboard that helps fix WPC pinball resets or my Williams system 3-7 sound board potentiometer solutions