A Facebook CNC guy I respect asked for another run of the box configuration with the rails mounted top and bottom.

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Deflection was 0.024mm. But the Z axis had to be extended downward to account for the increased separation between the rails. So the lever arm is longer and the displacement more. Depending on where the twist axis lies. Too complicated for the simplicity of the model. My personal opinion is the the rail placement is probably not much difference.

OK, now I am done. Gotta start a gantry layout now.

John C