Origin Live and Expressimo Audio both make variable VTA adjusters for the Rega arms. They are around $40. They are threaded adjusters, and not the easiest to use, but they do work. You can dial it in exactly, with a little patience and a good ear.
Generally, to adjust VTA, you start with the tonearm level while it is playing. Then, you put the arm back on the clip, and perform an adjustment, either up or down. Listen to the result, and determine if you went the right way or not. Make only small adjustments, and play around like this until you get the best sound. Different cartridges like different VTA, and you can only get it right by listening, and adjusting.
Generally, to adjust VTA, you start with the tonearm level while it is playing. Then, you put the arm back on the clip, and perform an adjustment, either up or down. Listen to the result, and determine if you went the right way or not. Make only small adjustments, and play around like this until you get the best sound. Different cartridges like different VTA, and you can only get it right by listening, and adjusting.