When the Baetis hatch is well under way and the fish clearly is feeding on duns, nothing beats the Baetis Parachute Paradun. Tied this way, with sparse and straight hackle, the fly rides low and gives a convincing print in the water.
You might replace the fibettes with Coq de Leon and the poly wing with CdC feathers. The the choice is really not important.
Although I love this pattern, I always bring a comparadun and extended body variants in my fly box.