The "halo effect".
Joe Always1stPlace says he uses the Thom McCan #11 wingtip for his super plane.
So everyone within earshot finds that shape and uses it.. and finds it is exactly what Joe Al... says it is.
Which brings up this.... way back when, famous desert motorcycle racer J Roberts (JR) botched a weld on his tuned pipe... rather than dress it out and redo it, he painted the area around the botch flat black.
At the next race, all the JR wanna-bes saw this difference, and asked about it...
Which brings up this... Dogbert says, "Beware the advice of successful people. They do NOT seek company!"..
So JR winged it.. about mid-range torque, horsepower, and other techno-stuff..
Anyhoo, the next race.. lots of tuned pipes with black bands just where JR said to put them, and ALL of the riders swore they could detect the "mid-range torque.... etc.."
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Now, JR, like JoeAlways1stPlace could take your (or my) best equipment, set up the way you (or I) set it up. and BEAT YOU (and me) with it!
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With the obvious difficulties in generating a true-to-contour airfoil, without access to precision CNC machinery that can manufacture a true-to-contour female mold for the wing. about all anyone can expect is to get close to a desired profile. What with the building inaccuracies that creep in, no one's wing will be much better or worse, when you try hard to do it right.
Any performance difference will be due to the PILOT!
Practice, in other words, makes JoeAlways1stPlace the flier he (or she) is!