Help sinking Destroyers

[Shado]

Hi all, a possible newbe question, but here goes. How do you hit a Destroyer? Right now I am running shiv, tmo 1.9 with patch and RSRD with patch. I am not using the manual targeting (not yet), I am working on the getting in position part before moving to the full manual targeting. I have come across several destroyers and have used the automatic firing, I don't lock the target, but let it set the range, AOB and speed. I set the torp depth to the minimum ( I think 3ft) and I have the event camera on to see how it works, and everyone I have fired at the torp has gone under the ship. It looks like I am getting into position close enough and the automatic is working, just can't seem to get the torp to run shallow enough to hit. I know the torps at this time period (December of 41) had a tendency to run deeper by about 10 feet (that is why I set it to the shallowest setting). I tried the same thing on one cargo ship, and it hit, not quite where I wanted but it did hit. Does anyone have any suggestions? of just keep trying and hope for the best or just ignore firing at destroyers and worry about the other ships Thanks