Outer ring - who uses and what are your findings

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

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.)

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.

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