More (small) progress. The plan had been badly "accordioned" in shipment and would not lie flat at all so I bought a foam board and stuck the plan to it using a repositionable adhesive. The nice thing about this glue is that, at any point, I can take the plan off the board and the tackiness stays on the board, not the plan. Now it's much easier to deal with and I was able to follow Radio Joe's advice and marked "stations" on the plan at 10cm intervals. I then transferred the markings to the hull, double checking each measurement as I went along. Next, installing the deck bearers and templates.
One question: in the 3rd photo, you can see a long strip of fabric glued to the bottom side of the hull (on both sides). I've searched the instructions but they seem to make no mention of it. I obtained some plans of the Starling from John Lambert and they show some sort of marking/structure at a similar point but I have no idea what they are or what to do about them. Any clues?
As always, TIA!