Problem is that RFB Natural Sinking Model seems to be bit ahistorical. Ships did often sink because of loss of balance, not flooding per se (IMHO). That is well-documented as is number of exploding torpedo hits to achieve sinking.
Now, hits to same compartment do not help at all, while in reality, they'd cause critical results quite often, up to breaking ship in two.
Something like
http://www.combinedfleet.com/shoksinknotes.htm
It often takes me 6 exploding hits to sing large freighter...which is way above historical numbers. I try to be constructive, instead of griping, tho. There obviously was large amount of work that went towards this mod and generally I have been very happy with it.