I am not sure I have ever fished them. I tied some a few years ago, and thought I would tie some again. Plan to fish them next summer.
I believe they are/were pretty famous for fishing the very difficult Silver Creek in Idaho. There, they have a similar pattern, but include an extension of the same material as the extended tail. I believe it is called the "Hatchmaster" and makes a convincing profile, in my opinion.
Some have commented that this pattern might twist light tippets. If I find a picture of the "Hatchmaster", I will post it.
Before hackling. Someone else's tie, Wally Wing Hatchmaster: