Excellent as usual Scott,

I suspect you have changed the body from floss to Uni Stretch. I don't think Uni Stretch was around in 1974. What difference does this make? I suspect Uni Stretch doesn't become translucent when wet. A yellow floss body over black thread will show olive when wet. I know colour is only of lesser significance in dry flies, but brightening a colour may have quite an effect.

Recently I tried an experiment with the Double Badger variation I tie for a shop. Usually tied with black thread, I tried tying it with Fl Fire Orange to see if it became more attractive to grayling (Many grayling flies have a bright tail). It does seem to be working so far, though we are still in the testing stage.
Petes Flees_0008-1.jpg
Cheers,
A.