The CdC Bubble emerger pattern is used by many. Usually it is tied on a curved shank or an ordinary dry fly hook. I have modified the pattern slightly, and tie a variant on a TMC 200R or Mustad C53S.
The profile of these hooks is more like the hatching profile for several of the mayfly species that hatch in open water. It’s flat, with a slight downward curvature in back part of the abdomen.
The CdC bubble ensures good floatablity for the fly. But be aware – you’ll need plenty of daylight to see it as it drifts down the river. This variant is tied as a BWO emerger/flymf.
Generally, I do not fish traditional emerger patterns during a BWO (Baetis) hatch. These bugs usually sit on the surface for a long time, giving the trout plenty of time to feed on the adult bug. Thus, they rarely get keyed in on emergers. Flymf patterns like this, however, seem to outfish traditional emerger patterns. It’s worth having one of them in your box.