Good to see you're back, Jan. I wrote you a long mail after your last PM a month ago, but I fear it never reached you, as I got a couple of confusing prefab messages. Never mind, your build is great.
I do have a suggestion. I see that you initially build your hull without stem, stern and keel. I understand why, but in this case I think something goes wrong. If you look at the first two or three strakes of planking, starting from the keel, you will see that they all have to end in the rabbet in the stern, called the `streek`. It makes sure that the stern is tightly connected with the rest of the body, both during construction and later. Adding your stern in a later stage prevents these planks to be fitted in the way they should. Perhaps this freehand sketch clarifies what I mean:
We are looking at the back of the stern. The thicker part caused by the planks only partly sunken into the rabbet will be continued in the rudder.