VTA is one of those things where if your arm makes adjustment on the fly convenient accurate and repeatable, and if you're a keen listener with a lot of patience, and time, then with enough effort you can learn to hear and appreciate when its perfectly dialed in. Unfortunately having done this the next thing you will notice is its slightly different from record to record. There's no real correlation with how thick or anything either. All you can do is listen.
Was at an audio meeting one time where not a single one of the 20+ there had the slightest clue about how to do this. In fact their suggestions were laughably off. So given you don't have the arm I would just relax and enjoy it. Otherwise you are looking at shims and a huge effort to make any difference and whatever you do will be obscured by the fact that shimming the cart is messing with vibration control which depending on how its done may swamp any VTA changes you might hear.
Time and money will be much better spent on springs, sand box, fO.q tape, PHT, and other stuff that will make a much more obvious improvement.
