IMO, the whole confusion between VTA and SRA stems from the fact that it is not possible to adjust one independently of the other. FWIW, arm manufacturers describe this adjustment as VTA while a corresponding SRA adjustment feature in a cartridge is not available. Regardless of what the geometric adjustment is called, the idea is to get the stylus to the correct vertical relationship between its edge profile and the grove of the record. While the -2 degree specification that Soundsmith insists on is a good place to start, the cutter heads on record presses may or may not hold that geometry. That's why an audible difference can be observed even between the 2 sides of the same record.
The issue of VTF is also a concern because it is affected by VTA. Physical adjustments have to made (e.g. changing VTA by removing the mat) to accommodate for the height of the scale tray relative to the combined OAH of the mat & vinyl. This is necessary to obtain a reasonably accurate VTF measurement for actual playback conditions. Every tonearm is a bit different, but a long-standing rule of thumb is to get the VTF set when the arm wand is parallel to what will become the vinyl surface. That will minimize VTA (inclusive of SRA) errors due to variations in vinyl thickness as well as minimizing induced VTF changes. As the OP has discovered, it's also a very tedious process in fixed VTA arms.
These points of geometry are precisely why I am such a big fan of VTA OTF capability in tonearms. Setting VTF becomes a rote task. VTA (again, inclusive of SRA) becomes something that can be unambiguously controlled in real time. It sounds better or it doesn't. Stop adjusting when it sounds as good as you can get it. The best arm and cartridge combos can resolve even minute differences to drive profound results.
Not everyone is willing to address all these minutiae simply to play recorded music, but the effort is worth it to me. That's why audio is such a great hobby!
The issue of VTF is also a concern because it is affected by VTA. Physical adjustments have to made (e.g. changing VTA by removing the mat) to accommodate for the height of the scale tray relative to the combined OAH of the mat & vinyl. This is necessary to obtain a reasonably accurate VTF measurement for actual playback conditions. Every tonearm is a bit different, but a long-standing rule of thumb is to get the VTF set when the arm wand is parallel to what will become the vinyl surface. That will minimize VTA (inclusive of SRA) errors due to variations in vinyl thickness as well as minimizing induced VTF changes. As the OP has discovered, it's also a very tedious process in fixed VTA arms.
These points of geometry are precisely why I am such a big fan of VTA OTF capability in tonearms. Setting VTF becomes a rote task. VTA (again, inclusive of SRA) becomes something that can be unambiguously controlled in real time. It sounds better or it doesn't. Stop adjusting when it sounds as good as you can get it. The best arm and cartridge combos can resolve even minute differences to drive profound results.
Not everyone is willing to address all these minutiae simply to play recorded music, but the effort is worth it to me. That's why audio is such a great hobby!