Before doing anything, I took the time to measure my spindle runout. The shop is not warmed up yet but approximately 1 micron on the taper and 1.5 or so on the flat at the outside surface using my Mahr millimess 1 micron test indicator. My cam lock holes intersect the inside relief so I could not take a reliable measurement there. I don't think I'll be touching it.
I then mounted my Bison 5C Collet Chuck and measured its taper runout at about 1 micron. At first I thought that can't be right so I applied a tiny force on the Noga holder and sure enough, very smooth and predictable movement so it isn't sticking. A good example of how I set it up to index on the lowest runout. Still holding great about 9 years after I bought the chuck.
Next I installed a hardinge 1/4" collet with one of my better endmills. Same runout at the base of the endmill but a bit over 3 out near the flutes 1 inch away. Perhaps that would get better with deeper engagement in the collet but then I wouldn't be able to measure at that length. I have no precision rods I would trust for this test. They are on my Kijiji/marketplace search list.
I confess that I can't get the indicator into position for a 90 degree measurement so the results might be very slightly worse. But given the very small measurement, I doubt I could see the difference.
Those results are all turning the spindle by hand using the rear spider.
Of course, the acid test is the concentricity and consistency across length of the parts I turn on it.
All in all, a whole lot better than I remembered. Another reason I love my collet chuck.