Nice Work, but ...
The Shoulderstrap is totally wrong!
You gived a officer a strap from an Engine Feldwebel/
Stabsbootsmann!
A Feldwebel (Seargent ranks) is a rank under the officers and normally never command a sub!
You can find the correct german Kriegsmarine officers shouldertraps
HERE!
Normally it should be a 'Leutnant zur See' or a 'Oberleutnant zur See'!
Nice greetz from the other site of the deep!