The excessive roll, might be from the CG_Height in the sim file.

This is one of those variables that is a double edged sword. Too little and things are flat and the boat wont roll with the waves very much when surfaced. Too much and their over the top, and you end up, upside down.

As i recall, a good way to test this to see the varying effects of the number entered for CG_height, is to setup a single test mission where your surfaced, with a 20 or 30 knot destroyer bearing down on your broadsides, 500 meters away. They will ram, what your looking for, is how the boat rolls with the ramming per setting. Enter a large enough number for CG_height and the boat might do a 360. A small enough number, it might just roll over 90 degrees.

edit:
Another thing to check is the depth charges themselves.
There is a variable there that dictates the force of the explosion. (was it Impulse?). Basically this dictates how much of the depth charge you can feel, or how much it shakes you. Enter a large enougn number here, and you can actually propel the boat in speed or send it down in depth via the depth charge explosion. Back in SH3, i entered a ridiculously large number (200000 or something like that) for this varaiable, and a depth charge propelled my boat like 20 or 30 knots underwater, just from the exposion.

People like to jack this number up for the depth charge shake, but there is such a thing as too much of a good thing.

I haven't really cracked this MOD open as yet. Not sure if I want to because of time needed to do it right. I suspect the changes to DC_Barrels is mainly force of the explosion being jacked up a bit but not to bad.
If DC explodes behind boat it does propel boat to about 5 knots if it was close. Backward if explodes in front of boat.
If DC is above you it will push you down.
if DC is below you it will push you up.
if off to side towards bow or stern it will turn your boat with little rocking.
if off to side centered, the Roll is a bit over the top. Almost capsizing boat.

If time permit I will look at the CG_Height controller and attempt to reduce the DC roll effect by about 25% from where it is now. Is this controller in DC_Barrels.sim or in the Submarine SIM? IMO the boats need to have more roll/pitch/bounce action when surfaced. they are far to stable under storm confitions right now. As I recall, Sober was trying to fix the Roll/Pitch/Bounce effect last year...

I like your testing method to verify roll effect.:haha:

Wouldn't the exact opposite effect these 2 options ?
When the DC explodes it creates a vacuum, which will then suck the uboat into it.

Just thinking! :)

Given that, id say, Go into the depth charge sim files first. The variable your looking for is explosion_range.

The default value, if Ubi holds true to its usual vanilla pattern is 40. In my own work, ive used a value of 55. Whatever value works for you will probably vary greatly as the roll is probably influenced by the CG_height in the boats sim file.

edit:

And yeah, how's that for file dependencies and why mod soup is bad! lol

LOL that was awesome game looks great btw.

First thing that comes to my mind is to tone it down via the drag variable. Leave the GC rather high, for a nice roll&pitch while surfaced, but set the drag very low surfaced and high while submerged, to act like some sort of inertia. Haven't tested it, though.

No. If that were true then a torpedo against the hull of a ship would leave a hole that peeled out rather than in. The shock wave spreading out from the depth charge pushes the hull in if it's close enough, and pushes the boat away if the distance is greater.
http://en.wikipedia.org/wiki/Depth_charge

Note the section titled 'Underwater Explosions'.

I think he may be talking about the upwelling effect after the explosion caused by all the bubbles rushing toward the surface dragging the water up with them.