I have sunk a few big merchants with one torpedo so far in my current career but they have all been with a shot to the stern of the ship. The torp are always set to impact.
You could give that a go.
But I will say something that is true i have never seen a ship sink the same way twice since i have been playing with GWX.
So it is just a matter of time i believe before you get a ship break in half and sink like a stone on you.
Happy hunting.
