Dumbass........doesn't he know if you're gonna tresspass you gotta be in full camo.

I know the state flower for PA is already the "Yellow-Faced Postedsignia" but they make ones that read "Posted and Patrolled" which I have seen in the woods and they look like they carry a little more bite to them.
It's tough when you are that far away, and my guess is that the people sneaking in know this as well.
Absolutely nail the next trespasser you find, and from what I gather it's not a job of the PGC to enforce, you need to call the State Police just the same as if the guy was trespassing in your backyard.

I'd invest in more new signs and make sure every other tree for the entire boundary was freshly posted as well.