I've always read and heard that for selective trout use Compara-duns and Thorax duns. Compara-duns show the trout an excellent wing silhouette and Thorax duns are more imitative than traditionally tied Catskill-type dries (let's ignore parachutes, no-hackles, and other styles for now).
But don't a mayfly's wings run parallel to their body instead of perpendicular like a Compara-dun's do? How does the Compara-dun show such a great wing silhouette? And, aren't the mayfly's wings and legs a little closer to their head than a Thorax dun's wings and hackle are tied?
Just curious about your ideas.
Joe