Well, I've just reloaded stock while trying to get TMO to work. I've played this a couple times. I've found:
At mission start you have a pre-selected course. I alter course about 20 degrees to starboard (more north-east), stay at periscope depth, ahead 2/3. This lets me slip in close, the screening destroyers don't seem to pick me up. I can unload all forward tubes and usually get 1 carrier (once I got a carrier and something else big).
Go ahead full and dive below the thermal layer, then slow to 2/3. Escorts get close but never seem to drop on me. I have time to reload, then come back up for another go.
The second time the escorts have a better fix. But they are all milling around playing dodge-boat with each other. Just for fun I have launched a torp into the mix to watch the scramble. Then I dive deep and sneak away.
Although once, when sneaking quietly away deep at 4x, with no contacts over me, I suddenly took major damage to the stern and quickly died...
After playing TMO for so long, it seemed too easy. My biggest problem is wanting to stay on external camera so much watching the battle.