Rising fish striking at duns as they float down the current seams is the holy grail of many a river angler's season. Either a well placed paradun or a CDC Dun will usually be my choices. The paradun will sit a little lower in the surface. The CDC helps an imitation to float onto the surface. Here's a little example with two CDC feathers tied in for the wing (as opposed to the fibres being spun in a split thread). Microfibbets for the tails here, although a version with Coq de Leon may be my prefered choice for very glassy glides in crystal clear water:



~Dave