Take a look at the plans on this website:
http://www.uboatarchive.net/U-570DesignBook.htm
Specifically, Plates 6, 7, 11, 12, 16, and 17. Considering the complexity of the compressed air, trimming, compensating, and ballast systems onboard a submarine of even
that era, it's pretty hard to imagine even the most elite U-boat crew achieving perfect trim at full stop.
Oh, and the numbers of valves, manifolds, air lines, etc. in the control room is frankly nightmarish!
