I suspect Lurker will be using the same uboat orginally modded by Nautilus42, that i subsquently retouched some of the damage zones on.
All i can say is that a torpedo middle of target, or anywhere aft of the control room area, has a high likelyhood of resulting in a very gratifying KABOOM!
(If you hit forward of the control room, hes libable to be a little stubborn

)