I almost always using salvo of 2 (tube 1 & 3 with type I and tube 2 & 4 with type II). But I m not using salvo to have one 1 hit on 2, I always expect to score 2 hits (even if dud torpedo happened...) or exeptionaly with salvo of 3 for Large Merchant and salvo of 4 for fast warship which deserve me to shot at (battleship, carrier, you know the fancy stuff
).
In the basic 2 fishs shot, my solution is complete in the computer maybe 30 secondes before I have to free the fishes so I'm ajusting angle less than 5 secondes before firing in a way that the distance between both torpedoes at the impact point should be half the target length. I m not use to notice the actual angle actualy... must be between almost null to 5 ° I guess.
I did my longer range shot yesterday evening, 1500 meters. Wasn t able to close more, that ship was moving 12 knots in an area were surfacing would habe been succide. The angle should have been really close to 0 I guess and both score a hit.