Well, I was inside the machine for most of yesterday - looks like one of my Z-columns wasn't even bolted down
Still, it does show just how nicely balanced it all is
I will re-evaluate everything once I think it is actually all square - there's way, way less movement with all the bolts in place
I am still interested in automated measurement/calibration though, but I think I will hold off buying an expensive digital-dial indicator until I can get my digital calipers to talk to my PC.