Mild destroyers, you say? No way
They are mean and alert.
Phew, I just barely escaped two destroyers hunting me for 3 hours (game time) in 1939, playing OM400. And I had no chance to even launch a torpedo. One of them spotted my scope and in minutes they were upon me, coordinated tactics. One stood still to listen and the other charged.
I am still repairing my aft torp room, with critical flooding, 24 hours after the attack. And this is just the beginning of the war