Hi Siara,
No worries, mate. Always like to help if I can.
Yeah, your shot of U 552 shows the rear light I am talking about. The only image that might be of help is of U 553, from directly behind -
I can't recall where I got the image and can't unfortunately improve on the quality.
Another image of U 552, very similar to the one you posted -
Note that the tower railings, the top of the L-shaped isolators and the area where the tower meets the deck are all black.
Oh, and I very much like your tiny rivets.
Cheers,
Dougie