Quoted from wdennie:
Try a playing field protector, it will take care of cupped inserts.
What he said. I bought a huge sheet of that plastic, enough to make 3 protectors, for about $40. Take off the bumper caps and flippers, make your paper pattern, transfer it to the plastic and cut it out. I made one for Night Rider. I actually cleared my Alladins Castle a couple years ago, that games a keeper.