Nice tutorial, with a good example of sub ramming by a cargo at the end of part II
The most difficult thing to do when attacking a convoy (after slipping through escorts of course) is to select targets so torpedoes will hit each ship in a window of time so narrow that no evasive manoeuvres can save them...
map contact update is an absolute realism-killer for me and all my manual targeting is made only through the periscop but that is just another story...