When getting in is risky, I let the first escort pass, and sneak by the wing DD (if he's there) at 20 m (2kts. max).
Then I get a good reading on the speed from the ships I can clearly see. Identify as many of the convoy as you can.
Open the tubes before you fire, and away we go, you already have the speed and types. Range, AOB may still be required here and there.
And I always try to seek overlapping ships
After the attack, and if the DD's aren't close yet, I slowly decent or if they are on to me, crash dive to the deeps. Hard turn and slip away, for now...
