The Rega's spindle is too short for most clamps to work. I only know of two clamps that can do the job: one is known as the "Pig" and the other one is from Ortofon. The Pig is shaped like a nipple and works great. The problem is finding one. I don't know if the company that makes them still exists. The Ortofon will work, but you have to file or sandpaper a few millimeters off the three plastic feet for the clamping hole to reach the spindle.
Happy listening,
Happy listening,