Todd,
Couldn't see the specific shot, as I didn't subscribe, but I have seen a
few spent stones. I don't know as that there is "one way" that the trout
sees them come by, more than likely they look for triggers. I would use a
hairwing pattern flush in the surface, and suspect that if the body size and
general color was right, the wing would seem vague enough to fool the trout.
I guess my entire philosophy of tying is based on creating a visual
impression, as opposed to a specific, detailed imitation. Then again, I am
not a trout, so cannot say specifically what triggers feeding or what things
appear like to the swimming/hovering fish.
Tom