Rich,
The fish in the avatar was taken on exactly what you are trying to create. I used marabou for the tail, large cactus chenile for the body and a few wraps of x-cut bunny for the collar. I've varied the design over the years with the same stuff everybody else mentioned. Was just admiring the way the fly looked and moved in the water the other day...lotsa wiggle.
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Chasing old rags 500 miles from home.