Hi Chaz,
Some thoughts -
1.The plates which hang off the Y axis (and hold the Y bearings) look weak as they cantilevered off the side.
2. How will you clamp the spindle? Are you planning on using grub screws? Not sure that is a good idea.
3. Are you only using 1 bearing per rail on the Z axis? I would use 2 per rail.
4. I would use 2 screws on Y to get the most out of a machine like this.
5. 2 screws in Z is worth looking at but it takes up Y travel and I think one screw is still pretty good.
I've also been working on a new design over the past few weeks based on the DMG Mori - here is my attempt so far:
Iso metric:
Attachment 16658
Side:
Attachment 16659
Top:
Attachment 16660
Y axis:
Attachment 16661
Box Z axis:
Attachment 16662
Underside of Z axis showing spindle clamped by front plate:
Attachment 16663