When tying Zoo Cougars, is there any advantage in using two mallard flank feathers instead of one feather? The feather appears to give an articulated motion to the fly by its cupped design, and I would think two feathers would increase the action of the fly in the water.

Also, has anyone tested the effectiveness of this fly by adding some red deer hair to give the illusion of gills? A friend suggested if I wanted gills to just replace the white calf hair underwing with red calf tail, but that seemed like a bit of overkill. Any thoughts?

Joe