Someone with more steelhead flyfishing experience can probably answer the question better than me but, particularly on the hang down takes, you want the fish to take the fly and turn back downstream where they bacially hook themselves. NOT setting the hook, and often feeding a few inches of line to the fish at the time of the bite, can be a challenge depending on how you normally fish. I guess pulling plugs provides a decent analogy where the last thing you should do is immediately grab the rod and set the hook.