@lewm
I follow what you are saying 100% and I've read those 3 articles several yrs ago too. It's nothing groundbreaking, its all easy to understand the Korf scenarios. Foz does not measure crosstalk really, it measures channel balance by:
1. Giving you a reading for each channel using tracks 2 and 3 from the AP Test LP. You can play each and twist the arm to achieve as close to same reading as possible. This essentially puts the stylus at 90deg to groove or in the center however u want to describe it.
2. You can then play track 1 of the AP Test LP and check the channel balance, theoretically it should read ZERO.
If that is done, basically you are done with azimuth. If you find that looking at the front of the cart it is twisted way off center then you have an issue with the internal guts of the cartridge...live with it or send it back to mfg.
Measuring crosstalk is a different process, I noted how you can use the Foz to see what the unmodulated channel is reading, which should be ZERO but it usually never is, there is always signal crossing over. I use the process with a DVM to measure crosstalk but have never needed to make an adjustment, as I noted. I realize this is not the same for all carts but again, the user can decide if they want to adjust for it.
What I will never do is set azimuth by sight using a microscope, azimuth is an electrical setting. If the cart is built right, yes it should be perfectly 90 deg and the cart body should not be overly-tilted, again if it is live with it or send back.
What Korg states about arms (Rega) that don't have azimuth adjustment I agree with 100%, that kind of arm will never be on my table.
We are good....Cheers