Runout really shouldnt be an issue if using as a probe for digitising as all that you are doing is making a point cloud and it doesnt really matter if it starts 2 thou or 10 thou out as the next point will be exactly the same and so on. The reason I am bothered about runout is I want to use mine as an edgefinder so it needs to be spot on true with the spindle.
Running the spindle with the probe might cause other problems such as the contact being lost between rods and balls as spring pressure is not much and it would obviously be out of balance if its not dead true.
Just my thoughts but probably not even worth the 2c you USA guys usually give
Hood