Arthur-

But if you' re checking runout at the ends, that will be VERY dependent on where you put your supports in the center. If the supports are only 10" apart for a 30" shaft the ends will be showing much more runout than if your supports are 28" apart for a 30" shaft.

Need to have some sort of standard convention for measuring runout on the ends, just like there is a standard for measuring runout in the center. Something like: " supports 4" in from each end, regardless of shaft length" . ?

Measuring the spine and center runout at a 28" span makes the overhang on each side past the 28" irrelevant. The shaft could be 28.25" or 32" and it should be the same measurement for that given shaft. But for the runout at the ends, then the overhang past the center supports becomes critical. Agreed?