Hi Tony,
I had the same issue and it made me recheck the placing of the frames but they were definitely as per instructions.
The top of the frames did not properly match the deck and were too wide in places and curved in too far in other places.
I thought it would not be a good idea to alter the deck to suit the frames. The frame tops can be filed back where they stick out and packed where they are too far in. When it came to the gunwales there were areas where it did not seem possible to "file the outer part of the gunwales following the inclination given by the upper part of the frames". The outer edge of the gunwales can be filed where feasible.
As the rows of first planking got near the gunwales, some off-cuts were used to pack out the planks so they would meet and cover the outer edge of the gunwales.
I had this trouble mostly with the aft counter that was much narrower than the deck.
View attachment 639947
Initially I glued, nailed and counter-punched the nails for first planking but then found that gluing was enough. The nails could be driven only part way to hold the planks until the glue had fully set and then they were pulled out.
The first planking was later filled where necessary and sanded to smooth it all out and it was made a bit easier by having no nail heads to worry about.