Being the hunted is one of the reasons I love NYGM. I've sat right here many hours trying to sneak away. Some times I survive, some times not. When you do survive, it's such a thrill, it makes the time spent well worth it.
This is also one reason I sail in a Type IIa. At depth, the IIa leaves a smaller signature than the VII or IX. Maybe you should try the smaller U-Boat and see if that increases your chance of survival.