Personally, I don't really plan an attack with aft torps in mind. Unless I get really lucky and am positioned so that a convoy goes over me and I have targets in front and behind. That is pretty rare though and is still tricky to setup quickly.
If I'm close enough to a target and am out of forward fish I'll go flank speed and spin around, cut speed or all-stop and try to get an aft shot in.
If a target is stationary I'll manoeuvre to use the aft tubes in order to keep what I consider my main armament, the forward tubes, for other serious business (i.e. if it's a harbour situation then using the aft tubes allows me to get out of dodge quicker as I'm already pointing toward the 'exit'!! LOL).
Finally as already mentioned, the aft tubes are my defensive protection in an extreme emergency when I need to try and strike out at a pursuing warship and I'm out of options!!
