I have had Rega tonearms on my VPI turntable (first the RB-900, and currently the RB-1000). Although the Rega arms lack provision for VTA adjustment, I have found Rega's stainless steel spacers between the tonearm base and armboard work quite well. I adjusted both the RB-900, and now the RB-1000, using a small level so the tonearm is level (i.e., parallel with the platter).
Since different manufacturers' cartridges vary in their stylus rake angle, the "ideal" VTA for the Rega tonearm will vary depending on the cartridge you use. Therefore, I suggest you set the VTA by making the tonearm level, and not worry about whether it should be 1 degree higher or lower.
Since different manufacturers' cartridges vary in their stylus rake angle, the "ideal" VTA for the Rega tonearm will vary depending on the cartridge you use. Therefore, I suggest you set the VTA by making the tonearm level, and not worry about whether it should be 1 degree higher or lower.