Most accurate way to adjust for correct vta on vpi classic 1

If your arm does not allow for VTA on the fly, it will always be different depending on the thickness of the record.  That's just part of analog. If things sound a little dull, you can try raising the back of the arm slightly or change the tracking force a bit.  The tracking force sometimes makes a big difference.  Some people cannot live with the variables present in the analog world - always obsessing about adjustments until it becomes a source of stress instead of enjoyment.  Just goes with the territory. 

Find a recording that people say is good for hearing the differences when you adjust SRA. Do a search here and elsewhere; there are a lot of suggestions out there. If you can’t find one, take a record of a female singer, recorded without effects, and listen to it over and over ’till you know it very well. I have used Joni Mitchell’s "Blue." Make sure it’s something you like ’cause you’ll be listening to it a lot.
Set your tone arm to absolutely level and listen to the recording a few times.
Read all you can about your cartridge and see if reviewers or users have a consensus suggesting tail up or down.
Change the angle in that direction a very small amount and listen to the whole record. You are listening for the voice and instruments to "pop’ making them more 3 dimensional. Do that again and again in very small increments. If you do not hear improvement soon go back and stay at level.
If your reading does not come up with a tail up or down consensus. You may have to do this in both directions.

Thank you people for your input. It is very much appreciated.