Ok folks, I've got myself the Schellboot-book, and indeed that part you call "bilge" looks defferent compared to the instruction sheet I've downloaded from the Airfix website, but since the model will be "in action" that doesn't matter much to me.
As for the other inaccuracys, I'll just have to wait and see when I get my kit
One of the things I noticed though is that in the book there is a side drawing of the S-7 with the comment that the crew added a machinegun on the front deck, the kit comes with this same machinegun, but represents the S-10.
Is it possible that more crews decided to add the mg, or is this one of the inaccuracies of the kit ?