Hiya,
Welcome Aboard
Well my preferance is to aim to intercept at a 45deg angle
I go in full pelt on the surface until spotted lol
Dodge any shells hopefully
Stay at scope depth and usually the lead destoyer comes after me, I steer to that at zero or there abouts, When close enough i let 1 fish dead centre and wait, Then as it starts it's zig-zag i fire 1 fish 30deg starboard of it another same degree port
Usually 2 out of 3 hit it
Then watch for other incoming as i get in front of the merchants and lay scope depth decoys not too many though if a destroyers caught up with me
Then stay in the convoy and pick em off
Saying this deep n silent when needed
Pretty much mainly what i do, Have tried a head-on deep stopped position showing my pointy bit to oncoming convoy, But then i seem to get found, If i do i high speed to scope depth and lay a decoy or 2 and then blitz into the convoy hitting 1st ship i can (always hoping for hits lol) and then use stern tubes if/as when needed
All different scenarios so just keep trying until you think you've got a working technique
Have Fun
Ciao
Def