[Crannogman]

NB that my mods are ISE, RSRDC, NMMO, and OTC; auto targeting.

In the past, I attacked convoys from 45degrees ahead, shooting high-speed torps from about 3000y while submerged. Recently, I tend to attack from almost abeam, surfaced at night, firing low-speed fish from ~6000y. This generally keeps me outside the escorts' visual range, although I think I have gotten rather closer at radar depth. Sometimes I will first attack the escorts with my deck gun from about 7500y, which usually lets me wreck them before they can close range and damage me. You can usually escape pissed-off escorts when you're surfaced at night, because they will look for you to be submerged at the source of the torpedoes, not a few miles ahead closing in on the now-abandoned merchants.

When attacking larger prey, eg the Shokaku's at the Battle of Santa Cruz Islands, I fire a ten-fish spread from about 7500y. That's usually enough to sink one, and then I race on ahead to reload and repeat. Obviously I waste a fair number of torpedoes and refit a lot, but it's worth it to bag a carrier or battleship