I'm also considering getting the outer clamp. I read a review and the reviewer said the opposite of Narrod. He said to get the clamp first, and then get the SDS, if you want. His logic was that the additional mass (something like 7 lbs. if I remember correctly) goes a long way toward stabilizing the speed. The next question, now that you have much more stable speed, is whether you are spinning at a stable 33 1/3. You may be able to get there, with belt adjustments and some form of power regulation that you may already have (Monster, PS Audio, etc.). If not, then the SDS becomes more important.
VPI periphery record ring for VPI Scoutmaster
How much of an improvement does the VPI steel periphery record ring make? Do you think it's worth the $500 US retail price? Or would it be advisable to first look for the SDS, then afterwards purchase the ring? I'll be using it on a Scoutmaster turntable.