I have to agree with you on your concern of the various tweaks to the DD's. I like the sensor config from RUB as it provides a more accurate error margin altho the dumbing down of weapons is IMHO not accurate AFAIK. I have set DC to 30m and reinstated shell damage to stock settings. I find this to be a most challenging encounter especialy with multiple ships and shallow water.
I have been trying different settings with AI Sonar settings as even with RUB the sensors can function through a DC pass. I have also been looking to find a means to use sunk ships as a decoy, they would have shown up as a signal for sure and sitting beside one, for instance, would easily confuse a sonar contact. Also heavy seas and thermal layers would have confused readings as well as the speed of the hunter.
In Sonar.cfg I am trying the current settings and have found a bit of success in that the hunter looses contact more quickly
;Sonar active.
Sonar range factor=1 ;[>=0]
Sonar fog factor=0 ;[>=0]
Sonar light factor=0 ;[>=0]
Sonar waves factor=0.5 ;was 0 ;[>=0]
Sonar speed factor=0.2 ;was 0 ;[>=0]
Sonar aspect=1 ;[>=0]
Sonar enemy speed=0 ;[>=0]
Sonar noise factor=0.5 ;was 0 ;[>=0]
Sonar sensor height factor=0 ;[>=0]
Sonar already tracking modifier=20 ;[detection probability modifier]
Sonar decay time=150 ;[>0] already tracking bonus decay, in seconds
Sonar uses crew efficiency=true ;[true or false]
I am unsure weither this has caused the discrepancy or my tweaking of the AI-Sensor.dat. I will test further..
Keep up the good work mate!