I use aft torpedoes as soon as I can, paying attention, 'cause I still am not that familiar with shooting in the opposite direction. I only use it for single merchants. Since I don't engage DDs I don't need to save one aft torpedo as a life-savier in a bad situation.

Excellent! As I am using a type IX as well I keep a steam and an electric in my stern tubes, even if I think I am going to use just a kind of torpedos. So in this period I am using stern torpedos to attack single ships; shadowing them and going ahead, then going to PD and getting in position to use the stern tubes... usually it works. I also use them attacking convoys after I've shot the bow ones. I keep one or two torpedos returning to the base, expecially in this moment in my campaign (june 1940), when the bases in France are not operative yet and I've to return to Germany.