I don't understand how changing VTA would alter/affect the Best Tractor's alignment.
Tvad, kindly bear with my somewhat leaden prose as I try to walk through it.
As an example, imagine changing SRA/VTA by moving the post of the tonearm up or down. Imagine the center of the arm's pivot fixed at the center of the post. (Some tonearms do not match this hypothetical.) Imagine the cartridge is correctly aligned to some known standard such as Baerwald.
Start with the stylus at a 90 degree angle to the horizontal plane of the record and the tonearm happens to be parallel to the record. Mentally put a stake in the exact spot where the stylus point sits.
Now, raise the arm on its post, which causes its pivot point to raise. The distance from the pivot to the stake has increased - the 'effective distance' (Pivot-to-Spindle + Overhang relative to stake) - has increased.
The length of the arm is fixed, so something has to give. The stylus point does not simply pivot at the point of the stake - it is moved/pulled rearward from the spot marked by the stake as the arm is raised. This changes its effective length relative to the presumably correct alignment marked by the stake, and thus changes alignment. Its not protractor specific.
The smaller the VTA change, the smaller the change to effective length, so whether a VTA change is worth a new alignment is up to your ears.
I think that's right.
Tim