PT:
Was thinking about your question......... I use a soft hackle for rising pupa. One of my most productive flies. As to the Diving Caddis: Once she is an adult the metamorphis is complete. So, instead of a different design for the diving caddis, why not just add some lead free wire weight to the hook under the upper portion of the body? Just enough to get it to sink.
Not pretty to look at, because the only lead-free "lead" wire I have right now is for big nymphs so it causes a problem in dimension, but it will surely get this lady down in the water column.
Or, tried one lashing the wire parallel to the hook shank.