I was just sent to patrol the Massakar Choke Point but I missed the ships that went through there because a few days later I got a radio message telling of many troop transports sunk by another sub.
I took a risk and sailed up to Manila to raid the harbor. I managed to pull approx. 20000 tons. The nice Nippon Maru provided half of that.
Finally, I'm getting Mk 14 Torpedoes to use instead of short-range Mk 10s.