Hello lonesome wolf,
I believe that I was the one warning about this toy masquerading as as a model. My reaction was to return the kit unopened after I saw the offending little picture on the side of the box.
At this stage I think you have two options continuing to build this model:
1) Cut the hull at the water line and make a surfaced diorama either at sea or in port. Or
2) Cut the offending center line Stoffbuchse for shaft and ruddershaft off, fill up the holes with Bondo or some other plastic filler. Make the filler stand proud of the hull, because you will be shaving and filing it off when fairing the hull. A lines plan is included in the book "Vom Original zum Modell: Uboottyp IXC" by F.Koehl and A.Niestle, Verlag Bernard&Graefe, Bonn. Tel. 0228-64830 ask for Herr Junge. I ordered my copy (DM19.80) including the Planrolle (DM78.00+ 30.00 s&h) some time ago. They have yet to arrive. You will find drawings of the shape of rudders, props etc. You will just have to transscribe the scale. If you are able to remotely approach the quality of the VIIC at finearts, I shall applaude you as an accomplished shipwright.
Off course there are always the other options:
3) build it as per kit instruction and play with it in your bathtub. Or
4) toss it into file thirteen. Cheers, :-) RB