If you read Phil Rowley, he can really help. His theory on hook shape is interesting: basically if chirons are coming off the bottom and staging to begin their ascent to the surface, he prefers straight shank hooks because they haven't started migrating upward (wiggling). Mid water or when the bugs begin to move from the lake bottom towards the surface, he prefers curved shank hooks to imitate the wiggling motion of the ascending insects. He also likes the idea of tying "redbutts" on the pupal patterns as they change from the larval stage to pupal stage which suggests the straighter shanked ties should incorporate a turn or two of something red near the butt of the fly. Even on the curved patterns, we've gotten in the habit of adding a little red at the butt of the fly. Grey/redbutts have become a staple pattern. Thin is important and therefor we use little more than 8/0 tying thread to make the bodies and coat them all with superglue to preserve the color and add durability.