I know its very exciting to get a report or even spot a convoy,the multiple hydrophone reports,the anticipation etc etc.
But once you decide to attack it its another story...
I usually get spotted by the DD but even if I don't, I manage to hit max 2 ships (usually 2 torps each) and then you have to deal with at least 2-3 escorts.
It will take some hours getting rid of them (if you ever do that is) and then get back to the convoy and attack again.
For me it seems a better option to attack single merchants than attack alone a big convoy.At least I can survive longer in the Atlantic.
On the other hand I always try to attack them if sea is deep enough (100 meters and more).Can't resist!
Maybe I am not good enough dunno...It's still March '40 and it looks difficult can't imagine how it will be in couple of years.
Regarding DD what's a safe distance when you are running in diesels?i usually try to be at around 8 km away...