TaskForce/Convoy Attacks Pre-1944 Advice Please

[TheRoadTrain]

Calling All Kaulins.......

I seek advice on approach to convoys in April 1944....
Have finally been granted the XXI,with Bells,Whistle's.

With the torpedo FAT II " Electric" Do I select the ship,then the pattern run in front of the boat or behind?

I not used these pattern torpedos, as I like the TIIIe very reliable, HOWEVER..... in 1944 the Destroyers pick me up much earlier on approaches and even at 180m,and wont leave after hours of hammering.
Was that the way of it in WWII