What do you plan on cutting with it? Am I correct that you plan on using 2525 ballscrews for the X axis. At that size you might want to look at a rack and pinion set up. Though that does require a bit more in parts of the set up over a ballscrew. Interesting design that is similar to ones that have been used by more than a few members of the forums over the years. Would I be correct in guessing that you have done some reading in the forums before starting this design?