Hello and welcome to our happy little place.
I am not a builder of U-Boats, I know they go under water and have
really cool logos of sharks and devils painted on the conning tower and
thats about it, but just wanted to welcome you and to say that your
English is far better than most of the people I work with, including
me, whom were born, raised, and educated here in the USA.
A couple of ideas, do a search here on FSM for the 1/72 U-boat, for
there are a few strings that discuss this model in depth. One
modeler has really gone to great depths (pun) in scratchbuilding the
forwrad part that you are questioning. Also, have you visted
U-boat.net? Really great place for finding answers to those
questions about small details.
Regards,
Scott