Yes.. always tone down your RL ambient lighting. That red light idea sounds good but then the wiff might think I'm up to sumfing :-)
What I always do, it go through the whole attack procedure. Right up till the moment I can ID the ship.
If I can't ID the ship I don't fire ... unless.
1) ship is in convoy
2) has no lights on (requirement for neutral shipping)
This also depends on what year it is.... Post '42 anything is fair game if not obeying the
International Rules according to the Kriegsmarine 