Quoted from kcZ:
I have the plastic but I was just questioning its use.
I stand corrected... it seems like HEP does put this plastic on all his games.
Looks like I will be installing the plastic tomorrow.
The general rule is that when something was there when the game was made, you generally want to make sure it's there when you do the restoration. It was there to begin with for a reason. (There are exceptions to this rule, of course...the Indiana Jones mode hole scoop being one big example.)
If nobody comes up with the answer to the screw question, I'll try to look at it tomorrow.