I usually put it out at the TIW, that way I don't have to worry about having anything sneak up on me (my FFG sonar skills aren't that great). There might be an advantage to deploying the nixie late in that you don't have to worry about the nixie capturing torpedoes that never would have acquired you in the first place. The disadvantage to that would be that a torpedo that might have seen the nixie first sees you first, and the zigzag is going to have to be executed successfully to get the torpedo to switch targets.
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