[BillCar]

As I mentioned above, you can do an attack run while doing the fixed wire method. I do it all the time. It does not matter what angle the ship is relative to you, so you can travel towards it from the front (almost head on), do fixed wire, and make your shot. If you need to turn more towards its track, well, hit hard rudder until you're roughly on the right track, and then fire. That adds a couple seconds, at most.

When I do it this way, it is rare for me to take more than a few seconds between getting the speed and firing the torpedoes. It is done in one run.

If approaching from behind, you're going to have to overhaul the target anyway to shoot from 90 degrees, so I don't see how that takes any more time, either. Briefly turn towards the ship. Take speed bearing(60 seconds or less, often times 20 or less). Turn the U-boat back to parallel course. Finish overhauling. Turn U-boat one last time. Fire. You're going to overhaul and close distance anyway, might as well get some immediate, up-to-date information while doing it.