I like the looks of this pattern. The CDC will provide just enough bouyancy to keep the fly in the surface film. Don’t treat the CDC with floatant. If tied in sizes 16 or smaller, the biot body could be replaced with sparsely dubbed body or pheasant tail fibers wound up as the abdomen. A small touch of sparkle dub under the loop of CDC will provide an attractant similar to emerging mayflies just below the surface. This fly works for BWO, PMD and Callibaetis mayflies. I am going to experiment with it for emerging chironomids.
SwittersB & Exploring 