In review of my last posting, I see that I made a obvious mistake. There is no set dimension for # 1& 2 as those dimensions are set by the user.
On a related front, in using the Dewalt 660 it would be helpful to know the following instead.
1. How much of the X to X rail Y distance is usable? Or how much is lost?
2. How much of the Y to Y rail X distance is usable? Or how much is lost?