I want a few millimeters of accuracy, but I also want repeatability.

We seem to be in agreement on a few high-level points.

You say there are "super-accurate" methods that are well-tested, in the thread you cited. But a skim (admittedly a sketchy reading) through it does not show me any testing, and a few of the suggested techniques do not say it's tested. Have you tested any? What reference did you use to check if the results are accurate?

And why do you jump to the conclusion or at least suggestion that what I suggest is not tested? How do you know?

I can confirm the data given in some of the classic bike catalogs, Trek and Rivendell. I'm happy with that accuracy.