okay, i have a happs coin door (over/under) and its a 2 player one. anyway, im going to cut the hole in the middle of the piece of wood in the front so i can mount the coin door. my question is, whats the best way to go about measuring for the hole? i mean, im not measuring the outside of the coin door, but the inner part, and that itself is curved on the edges. how can i be as accurate as possible on this? anybody have suggestions?