Here is the X-axis stepper mounted on the temporary MDF bearing support. After I drilled the holes for the standoff bolts, I put superglue in the holes before tapping them. Someone one on the zone (probably in the Router forums) taught me that trick. It gives you much stronger thread support in the MDF.
I haven't done anything about supporting the left end of the leadscrew yet. Given its length it isn't likely to whip much. However, after I get the machine actually running I will use it to make its own supports for both ends of the X-axis.
Alan