I hit a milestone with my CNC project tonight, I made my first cut!
Here's the current state of it configured for milling:
I'm using the Zen Toolworks 12x12 , F8 edition. The F8 edition has an extended Z-axis travel on the gantry, which is needed to be able to use the device for 3D printing. One thing I didn't realize initially were that: 1) configured as a milling machine, the spindle will not reach down to the bed, and 2) the extra Z axis travel does not benefit milling as much, because the gantry clearance is one of the limiting factors. The two possible approaches to address the first issues are to either re-work(ie invent your own) the spindle mount to lower it close to the bed, or to build an elevated platform as your new work area. I decided to do that because it reportedly reduces error due to frame torsional forces. I could always build a new mount and remove the table. The Zen is pretty flexible in that way, a good deal of the design can be up to you.