Do you mean adjust for square or adjust for depth?
If it's the former, I think I could just have the holes in the poly be larger than the bolt, giving a small amount of wiggle room for squaring it up.
Both. I've only used the WP sled, so it is my only point of reference. I prefer to set the router table fence with reference to the cutter and then set the sled with reference to the fence. At 9:04 in the video below, he shows how to set up the WP sled for a cut, and this is the method I use.