I like the idea of this pattern and have seen it around by others. I have tied maybe a half dozen and honestly not tested them enough to cast doubt or praise. A couple other more notable fly fishers have some opinions….

Tom Chandler at TroutUnderground has a detailed 2010 piece on this concept here….and Mick Hall of Kossiedun has put some effort into the reverse concept as well. Roy Christie has done a lot of work with it as well. Intriguing design concept though for certain. The three notables offer some inspiration here for experimentation. You don’t have to use the name I coined above.

Emerging Lambda "Compressed" Dun by Mick Hall