I'm late to the party, but I agree with this.
I think, even if the fish are in 30 feet of water, they are looking up at the sky and basically seeing a shadow that looks like a suspended, struggling minnow. They'll come up from 30 feet to get it.
I'm no expert, but because of that I think the leader dept and even the color of the fly are not all that important. If anything, I'd go shallower before I go deeper.




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