I'm only running the OTC mod for 1.4, with patch, plus ship pack 1 and hull numbers.
It's mid-March 1942 and I've just run up against my first surface HUK group, one DD, one subchaser (Chidori?) and of all things a gunboat. After detecting via sonar three warships at high speed where previously there had been only one normally encountered (except around convoys, of course), I figured these guys had been sent out by the head shed to deal with my depredations. They made a beeline for my general area, then slowed down, spread out and began executing figure-8s in the water. I was too far away to detect pinging and figured they had gone passive so went deep and quiet, and motored out of there. Will get a hundred or so miles away and wait a couple of days for them to get tired and then leave before I return to what appears to be a pretty good area - NE of Formosa.