thanks for the hints and replies! I finished the patrol last night, before making the delivery I intercepted a convoy - 3 or four destroyers and about 9 merchants/troop transports. I managed to evade the initial DD screen and came to PD in the middle of the merchants, initially sinking two troop transports and one destroyer who was standing still to find me on sonar
. Then came the depth charging but I think they only damaged my AA gun. I skulked around for a couple of hours, then sunk another slowly moving DD, surfaced and picked off a couple of small unarmed mechants with the deck gun before evading the last DD. Then I had only one aft torpedoe left and went very deep and rested until what remained of the convoy had passed my position. The whole thing was very exciting to say the least, took me 5 hours straight to play through this encounter
.
Mission complete, 5 warship and 5 merchants sunk (and 3 seaplanes). 20 something thousand in tonnage i believe. Now to find some carriers...