I relieved most of the tension on the X screws and now it's much better. Seems happy at 3600mm/min over the whole bed. I'm using a 42T pulley on motor, and the 28T pulley I posted about earlier on the 2.5mm pitch screw.

Bed surfacing, not terribly exciting but it demonstrates the vacuum working reasonably well:

http://www.youtube.com/watch?v=Jb1TL..._order&list=UL

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