I have attempted to adjust this by adjusting the screws slightly, Don't want to tighten or loosen anything too much though. And still it is off by about 5 mil.
The only thing I can think to do is to try to shim the towers in the tri-Supports. It really has to be the the tri-supports that are causing it, As I did notice it before getting the top on, I just thought I had it out before I squared everything up... but back it came.
If I run my square on the inside of the tower, it is square to the bed and top. if I rotate the square by 45º around the Z axis (parallel to the tower) the tower is square to the bed. But the twist is there. at 90º there isn't enough bed to really gauge it.
The only thing I can think of, is to Shim the towers in the triSupports to remove the torsion.
Any other Ideas? Hopefully better, as I don't know if shimming it would through anything else off.
BTW, I did search for the same problem, something similar was there, but the purported cause, does not look to be the same. They mentioned that some tabs were too long, and needed to be sanded. I don't have any tabs that are too long. Several that were too short, but the direction that they were facing, should also not be an issue.