Many Thanks Gilles for the additional information and comments.
The helm port framing is peculiar with 9 timbers to form a really massive solid piece extended that high in the center of the stern. In reality, I would think that these timbers should only be extended up to the lower transom: basically in line with the top of the red lines. But never mind, that seems to be the way the stern is framed in the kit.
You are right that this would not be so massive in real - I guess it is a reason of stability (of the fragile kit parts) and to make it easier for the modeler.
Usually it will be all covered by the outside planking of the stern.
The main question, which I did not ake into account until now is the inside view of this part.
As we know, the windows in the stern are no real windows, they are "fake" on the real ship.
When we take a look at Etiennes great model in 1:24 we can see where the level of the deck is ending - appr. in the middle (in height) of the "windows"
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also visible at the Jean Boudriot drawings where we can find a longitudinal cross section of the stern
Now it has to be checked, if these 9 timbers are visible (the 2 times 3 timbers) are shorter than the deck or not? ...... if they are too long, they have to be shortened and sanded down in such way, that they are not visble any more, after the deck planking is done.
Do not forget to cut the helm port before nailing. Right now you do not have an opening for the rudder to go through. Then, you can take care of the nails.
As for the nails into that solid piece (those 9 timbers in the center): I would only nail the planks to the center and the side timbers. That will give you about the right spacing along with the other vertical timbers. Nails should be installed around opening of the helm port as well unless you plan to install a rudder coat later.
I will take this into account and will make the nailing after opening the helm port - rudder coat is another challenge - I have planned it and the kit contents also some very fine canvas for this.....
Once more Many Thanks for the helpfull comments - Highly appreciated and welcome - so please visit my log as often as possible......