Doug, you wrote, "2.a. that adjustment beneath the VTA tower was mis-set by the manufacturer or altered by somebody. This is a job for Tri-Mai unless you're feeling brave. There's only one correct position and it's unclear to me (doing this from memory) how to measure or describe it. Even rotating to the correct spindle-to-pivot dimension might be wrong, if 2.b were also off."
I agree that there is only one correct position, but the qualification is that there is only one correct position for a given set of three mounting screw holes. Swinging the arm pivot with respect to the VTA tower could be corrected for by drilling a new set of mounting screw holes. I almost had to mess with that screw under the tower myself, because the lucite jig that Tri sold me was slightly inaccurate. (As you say, Tri told me NOT to do it.) I found that my older metal jig, that locates the tonearm by fixing the location of the pivot point, was more accurate. Anyway, I don't see why or how one could ruin the tonearm by rotating the VTA tower, but it's not for the faint of heart to do that. By the way, measuring twice with an inaccurate mounting jig will not help much.
I agree that there is only one correct position, but the qualification is that there is only one correct position for a given set of three mounting screw holes. Swinging the arm pivot with respect to the VTA tower could be corrected for by drilling a new set of mounting screw holes. I almost had to mess with that screw under the tower myself, because the lucite jig that Tri sold me was slightly inaccurate. (As you say, Tri told me NOT to do it.) I found that my older metal jig, that locates the tonearm by fixing the location of the pivot point, was more accurate. Anyway, I don't see why or how one could ruin the tonearm by rotating the VTA tower, but it's not for the faint of heart to do that. By the way, measuring twice with an inaccurate mounting jig will not help much.