Bed twist issues

After assembling the Jubilee I quickly realized that I would need to add mesh leveling for the bed.  In theory the jubilee can auto tram the bed with the 3 indepentantly drive z screws.  The issue with this theory as it hinges on everything in the machine being perfectly square as I will demonstrate below.

After leveling the bed the first time  I and a pretty ugly mesh which showed the bed with an extreme twist.  

At first I though it was the bed.  I took of the magnetic print surface and re ran the mesh, I had a smoother result but still the twist persisted.  Next I happened to have a 12x12 granite tile (You can get this relatively cheap from home depot) It fit the bed perfectly.  Now the mesh had a very smooth but still twisted mesh.

After pondering the cause of this I realized that if the bed is flat then the frame itself must have a twist.  The "twist" appearance comes from the tramming, the 3 tram points are 0 that is why once side of the bed looks flat and the middle of the opposite is at 0.  That way you can tell that twist in in the unsupported corners and know where to clamp the frame.  To verify this I measured all the corners Z heights which looked fine. I then measured the diagonals across the front (tool side) and back (electrical side)  and found a small difference. 

This is where you have to be careful  the twist is mirrored on the bed mesh, so if you have this issue to loosen brackets and re-clamp then re-tighten the low corner and the opposite corner across the diagonal.

Once I did both corners most of the twist was gone

Funny enough after I put the print surface back on and preheated the bed the mesh got a little flatter yet,  I am not sure the primary reason for that but I am happy with the results