So, I have this modified Ashford spinning wheel, and it has a fair amount of "play" in its various parts. There seems to be a relatively large amount of vibration in the drive train compared to the high end modern spinning wheels. The naive observer would look at it and assume that no part of it was particularly precise. On the other hand, it does insert twist very fast. It is very much the fastest spinning wheel that I know about.
However, the #1 bobbin whorl is 50.0 mm in diameter, and the various flier whorls range from 51.5 mm to 50.6 mm in diameter. That is a difference of just over a mm or just over 1/25" of an inch that will change the grist of the produced yarn from 5,600 ypp to 44,500 ypp. It is not something the casual observer is going to see, and even if they do see it, they will presume that it is simply lack of precision on the part of whoever made the flier/bobbin assembly.
In particular, if the observer, is assuming that the wheel was made to run Scotch Tension or Irish Tension, the observer will will assume an error on the part of the maker. Even a wheel maker accustomed to working with double drive wheels designed to spin (soft) first run woolens (1,800 ypp) will assume that a 55 mm flyer whorl would be better. And indeed, a 55 mm flyer whorl with a 50 mm bobbin whorl working on a effective bobbin circumference of 3 inches will produce a first run woolen yarn. However, such yarns will rapidly fill the bobbin, changing the effective bobbin diameter, so the DRS system is not very useful with thick woolen yarns.
In short, DD works better with fine singles. And it does work. With all of its shaking, my Traddy will spin worsted 5,600 ypp singles about 3 or 4 times faster than any modern out of the box wheel. And, when I do the measurements and math, it is also about 2.5 to 5 times faster than the best Canadian production wheel (depending on grist). I simple do not know of anybody else that can sit down and spin worsted 5,600 ypp singles at a good honest hank per hour, all wound off and blocked.
Some might say those hanks are not real pretty, but they are not folks that can come close to spinning a hank per hour themselves. They are not folks that weave with that grist of hand spun. The do not produce or use such yarns and do not have a rational quality standard for such yarns.
Those who can, do. Those who cannot, criticize.
By the by, the knitting is a bit "Irish"; very functional, but no jealous gods are going to come after me. (I was knitting during a movie, and the movie turned out to be better than I thought it would be.) The good thing about knitting in the dark is that you cannot see your mistakes.
A finished hank of such 5-ply is a good day's spinning.