Thanks Ralf,
I just thought that you might like the following mock-up I created to modify the Trumpeter's 5908.
Here are my suggestions how to modify the kit to make it look like U-2330.
starting from the top:
-sand down hatch and create opening on the top of the CT (that is left to interpretation as there are no clear pictures of the turm. I think I came pretty close)
-extend the bulge (I would suggest to go further than the front of the periscope housing: if you take a look at this picture, I believe that in reality it extends almost half way of the housing and also the slope is less steep than the kit's part):
-crate step's rungs
-sand down and recreate the handrails and extend them and curve them up to the top of the front hatch (feature, I believe, unique on this boat)
-fill most of the flooding holes, create a few new ones and recreate the access hatch (maybe just use different CT and modify the top?)
-no wooden deck
-only one rudder on the bow
-fill three flooding holes on the bow (U-2330 had only 3 instead of 6)
-recreate the sounding equipment "notch" in the keel
These are just a few suggestions, I'm looking forward to your building log!