Rgiffin,
I have been using those hooks for a couple of years now. I bought every size available and immediately tied up one dozen of a PMD pattern to take last year for Silver Creek and the Henry's Fork. They worked excellent!!! I can attest to the fact that when a prolific hatch is occurring, fish will accept these as a natural. Now, I cannot attest to the fact that they will invoke a strike when no hatch is going on, since I have not tried my patterns during no hatch activity.
I have seen a DVD of a Japanese guy tying with these hooks, using a split mallard feather for an exaggarated mayfly tail. I tie my PMD patterns with an extended body, with a split microfibrette tail. Its a two stage process, making first the extended body and then of course, tying the entire fly. Total time for me, would be about 10-15mins per fly.
Your pattern looks great!! It would fool fish on the Henry's for sure. I peronsally don't use that type of material for the wings, because it makes the fly rotate during casting, twisting the tippet and leader. But whether you use deer or mallard feather wings, you still get that problem. Finally, what I settled on for wing material is CDC. It is soft and supple and does not promote twisting during the cast.
There is a debate as too whether if fish keen on the footprint on the surface of the water that is made by the legs of an adult mayfly resting on the water, supported by surface tension. That is where these hooks come in. The parachute hackle represent the spread legs of the natural and form the necessary dimples on the surface that fish que on. The typical parachute patterns allow the body and tail to rest on the water, making it look artifical to the fish, when viewed from below. I'm not 100% sure if this is correct since I'm not a fish!!
What I do know is that the hook allows the fly to ride perfectly on the water!!!