30 or so years ago when I first got seriously interested in fly fishing and tying, I went to a fly fishing conclave in Dallas and saw a guy (I have no idea who it was) use a goose biot on the bottom of the thorax to achieve the same result of splitting and sweeping the hackle up. He tied it in, wrapped the hackle and pulled it forward. I remember him saying that mayflies had a "chest plate" and this technique simulated it. I have no recollection of him talking about the fact that the fly would ride lower in the water using this method, but that may be yet another thing I have forgotten. I do remember thinking how neat it looked.

Joe