Excellent work you're doing Le Bosco! Your ductwork is looking really good.
I'm sure you're correct, that the Germans were masters of improvisation. They had to be during wartime with supplies being scarce and sources being bombed on a regular basis. They wouldn't know what meterial was available from one boat to the next.
But improvisation I think is a hallmark of marine building. I have my own sailboat, and every time I see one of the same marque as my own, I always go to inspect it. I've never seen two exactly the same. That seems to hold true with other types of boats too. Superficially they all look approximately alike, but when you get close and look at the actual fittings, there's always differences.
You're building the same type VII C/41 from Revell that I am, although I've modified mine a lot to represent a different boat, so I'm familiar with the model. However, the splinter shield on your 37mm FlaK looks much more detailed than mine did out of the box. Did you add the details, such as the hingesetc., or have they changed the moulds at Revell? The shield on mine started out completely flat.
Not that it's stayed flat BTW. I not only added the hinges, I made them operating so the shield on mine folds, IF you unlock them by pulling the levers that stick out at the side and go to to the braces in the centre. I think my 37mm ended up about 75 pieces. Far more than the kit out of the box.