Hi Donald - sorry I can’t provide any testimonials one way or the other. On my three 2020s, I have the rings about an inch or so from the component end of the cable. They sound nice. They might sound even better if I tweaked their position but it’s something I haven’t done to-date due to a combination of laziness and inaccessibility to the back of my components. Same with the V18 speaker cables although I may try adjusting them soon as they are readily accessible (laziness is my only barrier). I tried to buy the Octava digital cable without the ring. My order was accepted but then I was told it would be X weeks before it was shipped; however, I was told I could have the ringed version immediately for a small upcharge (much less than the MSRP difference). Alas, I haven’t played the ring on that one either. I’m hoping that someone with more motivation than me will go through the iterative process of optimizing the ring location and make an OMG claim of the life-changing improvements. That might be enough to get me off my listening position.
Thanks for the information. My D333 is close to finishing break-in, and I will try the ring adjustment later. But there is no question that the system sounds better when the ring is close to the component.
With M1200, the ring on Dream2020 was close to 8" from the PZ wall. However, with D333 it seems the ring needs to be moved closer to PZ. Then there is CG LE too, and I settled with the ring around 8" from MU2 wall too (with M1200).
However, on a different day I like a different location. It could be due to D333 break-in, or it could be due to my mood too. Regardless, these rings make a very minor difference.
By the way, when I tried out Stealth USB cable, the T ring made a stark difference than power cords. So, you may experience more differences on your digital cable.
Thanks Donald - when you settle on a position for the 2020 ring between your PZ and 333, please let us know. Right now, my 4m 2020 cable ring is definitely closer to the 333 than the PZ. Based on your experience, I may try relocating it closer to the PZ.
Wait, you are okay. My Dream2020 is from wall to PZ. In that case the ring is closer to PZ.
But for CG LE, it is from PZ to MU2. In such case, the ring is closer to MU2, not PZ.
But let us know your experience anyway.
The ring in the right position can transform a Bose little box in a Gryphon Apex, especially on 1st April evening.
Oh schitt, you guys are going to shame me into moving my rings. I just never did. Laziness.
He who sets the Rings right may be called Lord! 
I was thinking more along the lines of what the Coneheads do with their “senso-rings.”
For Stealth PC owners who also have MU2 and PowerZone, try this:
Set ring of Stealth CG (LE) at 4.5" from MU2 wall to inside of ring
Then, set ring of Stealth Dream2020 (or V18) at 6" from PZ wall to inside of ring
Let me know if the focus on midrange is better. Of course, with a different amp you may prefer another location. For instance, on my previous amp I preferred the ring to be one inch further on PZ. If you have more than two Stealth with rings, you have my sympathy! 
Sigh, I have CG AG on my MU2, and tunerless Gryphon Vanta power cables providing power to my PZ. So I can’t help. I will move all of my PC tuners to 4.5 inches next week. Two on the Commander, two to the Apex, one each on the MU2, BACCH, and Ethos. On my speaker cables I can do the same. I will be stunned if I can detect a difference. But I will happily accept it if it exists and is positive.
Your system is at a level that many tweaks may not do anything, then you have BACCH too. Somehow last night my brain was more sensitive to the little change in vocal that I normally do not detect from my system.
For the last few days my system was just missing the pinpoint focus (as if the singers have wider mouths). At first I thought D333 may need more break in time, then I noticed the ring for CG is more than a foot from MU2. So, I moved it closer and surprisingly I heard an improvement right the way. I spent the next hour to adjust both rings to arrive the positions.
My wife could hear the midrange focus too so that was a good thing.