On Thursday, August 30, 2018 at 2:30:44 PM UTC-4, wrote:
...My old PIK-20 was a bit better with 400 surface than polished.
When it would drop off in climb, I'd scuff with 400 back about 4 inches
and the climb got better.

Hank! That's a hell of away to remove bugs!

I haven't see any other airfoils that showed that characteristic.

Only because newer aircraft owners won't let you try it.