Hi ddrgn!
I am playing (and testing) a lot with your DD-test-mission (your post no.5) while waiting for patch 1.2.5

. I use it for both, yours and Nisgeis´, DD mods; of course not at the same time.
So, here´s what I´ve seen:
After escaping the trouble

I surfaced when out of their view range. I turned and went back surfaced to them (after they ended the search). Using my deckgun and torpedos, there was no reaction of the DDs.
I am just curious and would like to know, if this is a general problem or perhaps a collision with another mod?
PS: I found out, that a collision with a DD won´t damage my boat; but that´s another story