GWX torpedoing tips?

[Sharkfood]

I have been a long time away from SH3.Only lately i noticed this great mod (GWX).I read the manual,but it doesn't help much in this sector.

I noticed that magnetic shots under the keel aren't so effective as they used to be,while impact torpedoes seem doing more destruction (even immediate sinking).Is this true?I much prefer under the keel shots.

Is there any tip in GWX that i should follow?Should i forget about under the keel shots and go only for impact?Currently i have a large merchant.One shot under the keel midship,one impact at 4m around the engine area and it's still sailing.The only differece is a drop in speed.In stock SH3,i used to take most C3 with one shot under the keel.With 2 they were 99% condemned.