Bodger
Let me make two points:
1) I am not belittling your method ..... just saying it is better than naught, but may not be good enough.
2) I have never centered the spindle on a K2F, so am no expert. That said, it does not mean I cannot think thru the problem.
As I see it, the problem is exactly like centering a dowel rod in a 4 jaw chuck, the kind with independently adjustable jaws. One has to center the part in one plane first .... say the jaws at 3 and 9 o'clock, then rotate the chuck 90 degrees and center between the jaws that were at 12 and 6 o'clock. Then do again to check.
I am befuddled how the "pros" center the magneto spindle. Most likely they screw a bushing into one of the high tension ports, and use it to hold a dial indicator. This centers in one plane only. Just as in a 4 jaw chuck, one must check in a plane 90 degrees perpendicular. Perhaps, some rebuilders do it in one plane and call it good enough. I do not know if one plane centering is the standard,, but I do know several persons, who found, after having a K2F returned fresh from a rebuilder, that the spindles were, in fact, off center (robs ss as reported in another thread, comes to mind first.).
We need DynoDave to chime in on how it is done.
Hope this helps.
Slick