Quoted from LeChuck:
His sheet doesn't seem lined up all that well though - e.g. a lot of the switches are off center in their holes.
I assume that there is variation from play field to play field. Look at holes around the flipper bat bushings. They are oversized to allow for variation. Same for the elliptical holes around the outlane rollover wires.
The thing to keep in mind is the radius of a 1 1/16" ball is 1/2". So if a protector is cut with parts of it being 3/8" away from a play field part, such as a rubber post ring, play action will not be affected. The problem with loose cutting with wide margins is that no one will like the look and would whine about all of the gaps.
With the first one I made for myself I worked very hard to cut to tight tolerances as I did not want it to look like a protecter was on. By the time I got to number 4, I was cutting fairly loose for a few of reasons.
1) It was easier to make.
2) Cutting loosely, or sloppy, if you prefer, did not affect game play.
3) After the new wore off I did not notice any of the open space between the protecter and the play field parts.
4) After the new wore off I do not even notice I have a protecter on no matter
4) Pinballers might come over and comment on the nice looking play field but did not notice the protector and did not notice any gaps do to loose cuts.
This protecter that you linked has a some big gaps along the out lanes and rails and in front of the apron. It does not matter. It does not affect game play and you will not notice as you are playing.
There are two things I would have done different with this installation.
1) I would have located the protector around the flipper bushings and wire rollovers so it is more centered around the rollover wires. This would mean getting out your cutting tools of choice and doing some trimming to shift the protector to the right. It would take some work to do. You would have to trim in front of the right sling shot and continue around the play field posts and kick out saucer all the way up on the right.
2) What I would like to do with this protecter is lock it in tight up at the two inlane guides up at the back. If they would make the protecter by not cutting out the material that the inlane guides would set on you could make all of your trimming adjustments and then lock it in tight with the 4 posts at the inlane guides and the rest of the protector would float free, never shift position, and never bow up.