Outer ring - who uses and what are your findings

Never tried an outer ring, I use a Mitchell eng record clamp which is supplied with a couple of different thickness felt washers to be used under the record. You can adjust the pressure of the clamp by how much you tighten it.
I have found it works very well for minimalist warped vinyl but if you have a really bad edge warp it does not help much.
Every time I look at cost of outer rings it puts me off...lol

I own an SME Model 10 as well as Michell Gyro SE. Michell’s clamping system works fine, but SME’s is state of the art. If a record can’t be flattened by SME, it should be tossed into the garbage and life goes on. It would have to be visibly warped and severely rippled on the edge. No one should be buying a record like that to begin with. No periphery ring will fix that. 

But regular edge warps are easily fixed by SME. As the clamp is threaded, the outer part of the record gets bowed towards and pressed against the platter. 

If you have any problem, or even exertion sensation, in lifting a 3-4 lbs outer ring, you should hit the gym. 3 lbs is plenty to flatten anything that's going to get there. In the Clearaudio system, the ring plops right on, perfectly fitted and centered via a lexan lip on the platter. That's less annoying to me than screwing in a threaded clamp, or fiddling with a reflex clamp. Also the vertical bearing is a magnetic suspension with 0 friction or contact along that direction, so the ring weight cannot cause any wear.

Another happy VPI Prime user with Stillpoints LP1 and Periphery ring.  I also have a VPI weight that came with the Prime, and on a VPI HW19 MKIII a older VPI Clamp.  The setup on my Prime, works the best, but they all work.

As I have not tried one these are just musings.
Surely one of the 3 to 4lb rings is only going to work on a tt with a generous platter weight and powerful motor?

I guess if you are in the market to spend $1000 to $1500 for a ring it should be presumed obvious your tt would be up to snuff to start with.