What angle should I set the VTA on my VPI turntable?


I can't believe after all these years, I am asking such a basic "analogue 101" question, but here it goes. I own a VPI turntable that has a "VTA on the fly" knob.  I thought the best VTA setting was for the arm to be 100% parallel to the record surface.  

However, based on some research, I am not so sure that is correct way to set the arm to achieve optimal VTA and correlatively, optimal SRA.  Not sure, ... but I think I have to raise the pivot side of the arm.

Any advice would be appreciated. 

Thanks.     
bifwynne
remember to use your protractor after raising/lowering the arm....the cartridge will need to be moved forward/backward.
millercarbon, then you need to adjust your VTA with each record as they are all a little different and you think you can hear it. Knock yourself out.
Read the number off the dial, write it down on the record sleeve, done. Next time you can dial it back precisely where it was, fast and simple as reset the dial.

Sounds like a lot of work and that puts a lot of guys off. But, how many hours, weeks, months of working and saving did it take to get the thing in the first place? Ever wonder why it is people pay hundreds of dollars for some guy to come tune their table and say it was well worth it? Ever wonder what it was they did that was so magical? This is it.
Needless to say this will not be worth it if you are unable to hear the improvement. But then how did you manage to set it in the first place?
I’m one of the contributors on vinyl asylum that posted pics with SRA measurements from my USB camera. The last time I did this I was attempting to set a Soundsmith Sussoro ES Mk 2. Peter L. chimed in and explained that there’s a tiny facet that determines the contact geometry that’s practically hidden from view, even with a USB camera. I could barely make it out, but only with the stylus raised, not in the groove. Seeing the futility of this effort, I went another route, starting with parallel and then fine tuning with Analog Magic. I am NOT one to fine tune VTA/SRA for every record and my SME doesn’t have that provision anyway.
Just for kicks and giggles, I bought an Elvon "LP Vinyl Record Player Measuring Phono Tonearm VTA/Cartridge Azimuth Ruler."  The kit comes with a super light and super small bubble-level.  Dirt cheap too.

I also rooted around for the box and instruction that my Lyra Kleos cartridge came in.  Lyra recommends that the tonearm be parallel to the record surface and then small adjustments from there.
 
To my surprise, using the cheapy Elvon azimuth ruler and bubble-level, it turns out that my VPI tonearm was slightly out of adjustment.  Azimuth was off by a teeny amount and VTA was off by more than a small amount.  So I adjusted the tonearm and double checked the VTF.  I tried to compensate for the weight of the bubble-level too (about .25 grams).  Although not perfect, I checked my adjustments with the azimuth ruler and then double checked VTF and azimuth again with the bubble-level.

After all is said and done, I think my tonearm is for the most part parallel to the record, but I lifted the back-end by a smidge.  Hardly noticeable on the bubble level.  I thought the lift improved the sound.  It also was a rough justice compensation for the weight of the bubble-level.

After fiddling with the adjustments, I played some favorite LPs and was pleasantly surprised.  There were noticeable improvements in imaging (real sharp), soundstage (better centered and less smeared) and SQ.  All around noticeably better.