MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
If you have any tension then you have over tightened the braces.
When you install them without the screws the upper arms should be "loose". Now turn the screws AND NO MORE until the upper arms are no longer loose and the upper portion of your frame can no longer move in x-axis direction. Any further turns on the screws will cause tension on the frame which is not necessary and you don't want!
Of course the assumption is that the parts you printed came out in the quality and tolerance as designed.