This should help you out with the destroyers that see all...
Go into the SHIV directory under Data/Cfg and open the Sim file using Note Pad. Make sure that you open the Properties for the Sim file and set the permissions to allow for all users so the changes you make to the file will save.
Once there you'll change Hydrophone and Sonar settings to look like this:
[Hydrophone]
Detection time=5 ;[s]
Sensitivity=0.15 ;(0..1)
Height factor=0 ;[m]
Waves factor=0.5 ;1.0 ;[>=0]
Speed factor=12 ;[kt]
Noise factor=1.0 ;0.35 ;0.25 ;[>=0]
Thermal Layer Signal Attenuation=3.0 ;[>0], 1 means no signal reduction, 3 equals signal reduction to 33%
[Sonar]
Detection time=5 ;[s]
Sensitivity=0.05 ;(0..1)
Waves factor=1.0 ;[>=0]
Speed factor=15 ;[kt]
Enemy surface factor=200 ;[m2]
Lose time=15 ;[s]
Thermal Layer Signal Attenuation=5.0 ;[>0], 1 means no signal reduction, 5 equals signal reduction to 20%
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