Azimuth 2020

Robert, You wrote, "I pull out the test record and do a high frequency sweep to make sure channels are matched."
Matched for what?  Balance or crosstalk?

Matched for output level on a high frequency test sweep. If the azimuth is off, you will get left to right output level variations as the frequency changes at high frequencies.

Yes, but changing azimuth will also alter crosstalk, and azimuth has far less of an effect on channel balance vs crosstalk.  So a little change in balance makes a big change in crosstalk relationships. 

Azimuth has a significant impact on channel balance when you start looking at frequencies out past 10K, and especially past 20Khz, which you can get on the Ortofon test records (and Denon if you can find them).

If you balance the crosstalk, so it is the same on both channels, then your azimuth is likely off. The forces are slightly different for the left and right channels, even with perfect alignment and that contributes to slightly different crosstalk. If you balance the frequency response, then you are getting consistent groove tracking on both channels.

Nice coherent explanation of your viewpoint.
Thanks.