Outer ring - who uses and what are your findings

Best way to flatten records is an SME style of system. Screw on clamp with a specially shipped bottom and a washer under the record.

25 or so years ago I had an Ariston TT, the "minimalist" round one (RD40?) which used that method. Very effective. Since then, I've made very simple mods to a clamp that accomplished the same thing: total flatness. It must be a clamp, not a weight, as it needs a positive grip on the spindle to hold it down.

I have a VPI SSM and use the outer ring clamp on every lp- the extra weight "bonds" the lp to the platter very effectively and the peripheral mass seems to even out even the slightest speed variations.  I have a wooden thread spool on the side of my rack to hold the outer ring clamp when changing sides or lp's.

I use the VPI outer ring with the Stillpoint LPI. The combination is anything but a waste of time. 

Complete waste of time and a lot of money. Best way to flatten records is an SME style of system. Screw on clamp with a specially shipped bottom and a washer under the record. After getting my Model 10, I no longer worry about warped records. 

I used the Clearaudio outer ring and centering spider for years on my Clearaudio Champ II. I would say it worked to keep records with slight warp flat. I don't use it anymore. Sold it. I haven't missed it and wouldn't spend more than $100 to buy another. I don't think it made any difference in sound quality in my system. If it did, it was so incremental that I didn't notice. Warped records is certainly not the weakest link in my sound chain.

I have one for my Kenwood L07D.  I don't routinely use it, but when I did use it, I placed it directly on the platter edge, UNDER the lip of the LP, so that I didn't have to remove the ring every time I played another LP, with the attendant risk to the stylus. 98% of the LPs that I keep and play routinely are already flat; for me the ring is only to add peripheral mass to the platter to increase inertia.  (I'm not saying it wouldn't work to flatten a warped LP and perhaps to dampen resonances; I'm just saying that it's an aggravation and a risk to use it that way, and I don't feel I need it for that purpose.)

Thought about buying one for my Prime but it would just be one more thing for me to obsess about. 

It works.  Have made it part of my "ritual."

That is why I use one and it works.