ASW-24

Yes.
Chip, Hank and I were at a contest in Elmira many years ago. Chip was not convinced about winglets for the -24 yet.
We had an off day, so testing insued.
Chip flew his -24 with an early "Nixon slip on winglet" (no wing cutting needed), I flew Hanks -24 with an early Nixon winglet that required cutting the wing and Hank flew his -20 chatting and watching from behind so he could see.

We did straight runs at different speeds to check glide as well as thermaling with Chip and I alternating who led.
Minor gains on the later winglets vs. the slip ons, both were better than no winglets.
The big difference was in, "Yank and bank rough thermals". I could fairly consistently turn inside Chip in a hot spot and get above him.

So yes, stock vs. Nixon slip on or cut the wing was better with a winglet. Later "cut the wing" Nixon winglets were even better all around.
Not sure if they were tested against other brand winglets, likely, but I don't remember.

AFAIK, Chip may still even have those slip on winglets........

I recall that day very well, Charlie. I had been uncertain about winglets only until KS outclimbed me in a survival thermal at Littlefield with early Maughmer winglets when my ship was new. Once I started flying with UH's "slip on" winglets a year later, there was no going back. I could outclimb non-winglet 24s (and many other types) but the big difference was better low-speed handling.

My impression was that these early UH tips were better than the factory's. On more than one occasion, I was able to climb away from 24s with the factory winglets in weak thermals where I was pretty sure wing loading was not a factor.

It's true that on that day, Charlie was able to climb through me pretty convincingly with a later version of UH's tips. But the cross-over point in glide on that early developmental design was a little too low for me (75-80 kts?).

However, UH continued to refine his design and the final version retained the superior climb with no perceivable loss at the high-speed end. That's when I made the switch. I've been flying with them for 15 years and consider them essential. They're also Schleicher approved, now.

Chip Bearden