Bob, I assume you meant you were locking your gibs to INCREASE regidity
Unless I really tightened the gibs screw there was a lot of movement in the head (at least .005 in one axis) when I locked the gib. Surely if locking the gib is moving the head then maching forces would as well.
This weekend I plan to pull the head off and get a better idea of what is actually going on. The current idea is, after checking if the head modification would help and checking the acme screw in general, to hang some weight off the bottom of the head slide. Since I am using my machine in a manual mode I am not worried about motors driving the extra weight. Since I am using the acme screws there is quite a bit of backlash and since I had to tighten the gib down pretty snug to take up the head deflection the head sticks in places. It would seem that the addition of maybe 50 lbs hung off the bottom of the slide would help to overcome the sticking and keep the head firmly down against the acme screw and lock the gib when I want the Z to stay put. It would seem that unless the jib is locked that without a ballscrew and motor keeping it in place the head could wander down. Anyway, if the extra weight does not do the trick then on to trying a counterbalancing system.
Regarding the quill - I going to leave it up and locked down snug - my HF drill press is actually better. For z-axis measurement I guess I will mount a caliper on the column. I don't want to spend the cash on a DRO for this mill until I have more experience with it to know if it's justified.
I can understand now why some call the import mill/drills "mill kits"
I am sure it will be nice after all the kinks are worked out however.