Well I'm a BIG BAD BOY and I changed the power of my torpedoes and my deck guy (One shell=One split merchant:p). I have been thinking on modifing the power of the flak gun, but I believe it would be difficult to manuever into possition and get a good shot.
In general you might sink some, but it's a waste of ammunition and time.
Stick with good old eels or your deck get
(that is before it gets to dicy to stay on the surface)