Reduce AI sonar?

Hi

Even if i go down to 120m and constantly turn, a mark I destroyer in 1941 will pinpoint me exactely, set charges to right depth and pretty much kill me in the first run more often then not. Which is annoying since if i stay closer to the surface its even harder to survive.

1. Can i tweak the efficiency of enemy sonar/pinging?
2. Can i increase the damage i can take before i die/everything is flooded?

I know this might not be historically correct, plz help me anyway
Erik