Try grid squares AM 51, AM 52, AM 02 & AM 29. You should run into something in one of these areas as they're heavily travelled. Watch yourself if you go in to AM 53 (use low time compression). It's shallow & I've seen quite a few enemy task forces spawn nearby.
BF 11 through 17 seem to be good areas too. Be careful in BF 13 though. That area seems to be heavily patrolled by British ASW craft. I frequently come across those nasty little MTB's there.