Finally reinstalled Silent Hunter, with GWX for the first time. Ran a couple patrols just to reorient myself, then decided to try a 1939 career. Stuck myself in between the entrance to Dundee and the Firth of Fourth, waited for the war to start. After a day or two, hydrophones pick up a merchant ship approaching in just the right way. It's night and stormy, but he helpfully left his lights on, being ID'd as a medium cargo passing about 1.5km off my bow. I let loose a pair of torpedoes and both strike home. I couldn't resist passing close enough to admire the wreckage as it settled, the flag just barely peeking out from the waves. The Norwegian flag.
So now I've started a 1940 career, and other than letting a Revenge class get away after two torpedoes to the side on my second patrol, everything's going much better.