From the designer, Pat Weiss:

While the Hi-top caddis works quite well as a stand alone dry fly, it was designed as part of a long distance dry-dropper rig. Its purpose was to deliver a small Firefly or BP perdigon properly at distance. This requires a fly that floats well with out excess bulk or weight and doesnt push too much air during the cast. It works quite well on a euro dry-dropper as well. Tied in several color combinations, it gets eaten surprisingly often when no fish are rising.