I think the reason its so hard to find developed tactics for the late war is because in reality all the aces had been sunk or had been promoted to a desk job and all the noob captains were getting sunk after a few patrols.
Late war is really a hopeless situation. Without homing torpedoes and the snorkel it wouldn't even be possible to do anything.
I think that late war tactics are desperate and completely individual. Really late war survival came down to how smart and how realistic a captain you had. Anyone trying to coin tonnage would be dead before they knew it.
I think that surviving the war is a matter of extreme conservatism. Take the chances that appear. Fire from maximum distance and get as deep and as quiet as you can before the torpedoes hit. Submerge during the day with a snorkel and keep the flak crews manned at night while you're surfaced. I'd also suggest always having decks awash to seriously cut down diving time. Make sure you have at least one qualified repair officer and if you keep fatigue on be careful to not have your guys fatigued unneccesarily.
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