I'm sure this has been discussed before, but a search only turned up these photos
http://www.cnczone.com/forums/showpo...41&postcount=7
My guess is the largest source of fore/aft flex is the way the column attaches to the base. Ideally the column mount casting would would extend to the back of the base and the base would be slightly longer also.
If my guess is right, the brace idea makes a lot of sense. Building in a slight amount of adjustability (sp?) might be a good plan. Or maybe a bit of shim stock will fix any misalignment. Is there any advantage to retaining the large cupped washer with this design? Probably safe to do away with it.
Coincidently I just bought a 2'x4"x1" chunk of aluminum for a dual-purpose brace/ballscrew-mount. That square tubing will be much stronger.
Anyone who says "It only goes together one way" has no imagination.