Moving on to the inner planking, it seems there is an error here somewhere.
So let's assume you believe this plan, specifically that the #12 inner plank should end butting under the horizontal measuring sticks (red squares). This seems pretty reasonable.
However, I transcribed the plank heights to a piece of scrap paper. As noted in Uwe's log, planks 1-4 fit snugly together and so do 5-12. However, there is a suspicious gap between planks 4 and 5.
I then pressed plank #12 into place, butting it against the horizontal measuring sticks and drew a line where it intersected the frames. Using that line, I positioned the scrap piece of paper and marked off the location of planks 1-11. The marks weren't perfectly aligned due to the width of the planks, so just to be sure I fitted planks 9-12 and traced their lower edge. Then did the same with planks 5-8.
This leaves a rather large gap on the bottom of the frame, enough to fit 6.5 planks (not 4).
We know there is a limberboard in there but there's still room for another large plank. This is probably the missing plank "d" depicted on the Boudriot plans.
The correct way to plank this would probably be planks 1-4 (in order), followed by planks 12-5 (in order). The the missing plank D has to be hand cut and fitted.