I have caught many trout on dry flies down to size 24 and 26. And only a few were trout over 18 to 20 inches. I had one of the best few hours of dry fly fishing of my entire fishing life, on the San Juan River one autumn afternoon, on a size 24 blue winged olive and 7 X tippet.
This reminded me of this:
https://joetheauthor.wordpress.com/2015/03/29/joining-the-2020-club-at-last/