A question: since dry fly wings are vertical- or nearly so- above the water, why so much concern about the material's "floatability"? I've often read that a Wulff-style dry fly floats better in part because of the hair wings. Bushy hair tail? Sure. Heavy hackle? Absolutely. But high-riding hair wings? I really don't think so. Thus I choose the material(s) for my post wings, for example, by how they look to me, and how easy or hard it is to wrap a parachute hackle around them. Just my $0.05 (due to inflation).

Chuck