very nice work, indeed!
Some educated(?) guesses regarding the AA-fit of the 1944 version:
I doubt, that a 2cm on a submarine-mount would have been used.
Using the 2cm on the single mount c/30 would be more plausible imho.
(iirc some tugs even used captured enemy guns?)
"Kriegsschiffe 1815-1945" by Gröner states, that two MG were mounted, but I'm not sure about the MG34 twin-mount, that you've used.
Only ever seen those by the Heer and on E-Boats.
My guess would be two single pintle(?) mounts.
A bit hypothetical, but by '44 the ship would almost certainly have been camoed.
Might want to check these sites for some plausible shemes:
http://modellbauer.forumieren.de/t2252- ... hmv-verlag
http://www.steelnavy.net/SSNModellbauHe ... stelo.html