For a real challenge, try playing by turning off auto TDC and manually inputting target data (I do this when playing SH2 and Pacific Aces).
US S Class subs used the Mk 1 Submarine Attack Course Finder ("Is-Was"), and the Torpedo Angle Solver Mk 8 ("Banjo").
http://archive.hnsa.org/doc/attackfinder/index.htm
http://archive.hnsa.org/doc/banjo/index.htm