The hull array detects lower freq tonals than the bow array so its able to pick up targets futher away, the downside is its washout speed is lower than the spherical array.
You could try a course change right after firing so you have time to reacquire the target before you're fish go active.
You also might want to consider use of active sonar to locate the target for your torpedoes, if the party is on and the other guy knows where you are there is no point in remaining silent.
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