The largest rainbow trout I have ever brought to net was a thirteen pound behemoth (http://www.myoan.net/fishing/weight_calc.html) that attacked the Spruce Fly at a Central Oregon lake. I have found streamer use to be a personal preference point. All manner of streamers, some looking to be exact creations of baby rainbows, brook, browns or tui chubs and others, like the Spruce Fly or Mickey Finn, appearing to be more of an exciter or stimulant fly. As always, presentation of the fly may be the key. At Central Oregon’s Hosmer Lake, one can see flyfishers stripping white, pink or orange streamers to Brook Trout and Atlantic Salmon on cold October mornings. The flies represent, by their appearance, nothing in that lake (no not a crayfish) and the presentation is the key. An exciter/stimulating stripping action suitable for Trevally at the edge of the flats. So, the Spruce Fly works great at that moment when big browns, char or rainbows are on the hunt. Sizes 2, 4 and 6 on a 3x long hook are appropriate. Also, the wing placement is the key to this fly. They should not extend to far back and should be splayed (curved side out to gain that affect). Tie it and try it when stripping streamers to the big ones! Fly tied by Tony Muncy at a flytying expo a few years ago. Fortunately, he tied plenty to share while preparing/practicing for the show and during the show.