Right, in the end it’s largely guess work, probabilities, and subjectivity. And our approaches are not so dissimilar. I know my VTA dial settings for 180 gram and 140g LPs; I split the difference for 160, subtract that split from 140 for 120g, add it to 180 for 200. It’s a momentary mental exercise. I can approximate the weight of the LP by its flexibility via a quick shake when I take it out of the sleeve. It takes all of three seconds to set VTA with most of my arms, and I do so before I play the LP. None of this is rigorous scientific practice, but its close enough. Then I sit and enjoy the music. Like you, I’ll tweak it if it sounds off, but I usually do not need to. If I want I can check my work on my 2 Grahams because they have bubble levels. Most of my carts like the arm level--or I’ve conditioned my ears to believe that. There’s actually very little fuss in my process, and it lets me relax into the sound. As I mentioned, though, if I forget to change, I usually notice.