John, I have the highest admiration for the folks who just know all the things it's taken me years to either hear when told, or figure out. They may seem obvious, but until it rings true for me, I meander all over the place, for decades. I have an exceptionally long learning curve, but I can get there. Mountains of flies tied with what seemed appropriate bodies or hackles or hooks, whatever, and then it all shifts when I finally get a key concept clear. I may not be the worst offender in that regard, but I certainly among to the top in the field.
That's a great Hendy pic. I'm pining to get on some water but your post has put the wheels in motion and now all I'm thinking about is wing length and webby hackles and hook gauges. I love this stuff.