That's what I thought. The precise point 150m away seems very relevant. I wonder if anyone's just tried shining a light at it from that point?

Exactly, if he made it that kind of shape it's about the shape being the last part to the 4th part than anything else.

Maybe the 4th puzzle is actually the whole thing should be wrapped around. And it's not 97 characters but instead the resulting number of characters of all 4 square puzzles?