I've been tying a bunch of these little buggers lately...
Depending on the number of insects on the surface of the water, I like to fish this mayfly spinner as a dropper fly both on the surface and below. I like to go the opposite. If there are a lot of insects floating spent on the surface, then I fish this fly as a drowned BWO. If there are only a few mayfly spinners on the surface, then I float this fly. I want the odds in my favor and don't want my fly to compete with the hundreds of real spinners available.