If you can lower the ball screw and cut as little as possible I think you will be better off. The reason I say this is because of stress in the metal. It might try to move on you and cause your dovetail surfaces to be off a little after a lot of machining (think of the saddle trying to curl after taking out a bunch of metal). Chances are it might not, but the more metal you take out the more chance it has of doing so.
Jess |