Al Troth told us (at a Bozeman fly tying seminar) you have to work on a new pattern eight hours a day for a minimum of three or four days to get it right. I tend to morph that into one hour a day for a week or two. Green Drakes range 16mm to 20mm long. Or about 13/16" thirteen sixteenths of an inch long at the biggest. The extended duck flank tail on this one decouples fly size from hook size, which makes it possible to use a smaller hook. #18 scud hook dyed duck flank abdomen cdc wing dun hackle tied in no wider than the gape of the small hook, so the abdomen kisses the surface tension for most of its length, as does the real bug. Green Drake imitations tend to get complex and difficult. This one does its best to keep it simple.