I know a dude who frequents our usual route. Racer that showed me his oval rings just this Sunday. He said he loved them. Showing me some tips on how to set them up. He had scales on his ring allowing him to set at different values. I didn't really understand but he said something about having them set at 14 or 15. Each value differed in efficiency. I really don't know but they scale marks are there for a reason.
He is number 18 out of 20,000 on my favorite 7 mile segment of Strava. He does continuous solo 35 mile rides at 23 MPH.
I averaged 22.9 solo at my best on that segment. His average is 28 mph. Maybe I need some oval rings too.
I'm guessing he knows how to get the best out of them. I've never heard any other person mention the scales and setups.