Just finished competing in the Sauna Sail with a 25 year old wooden boat fitted with a kite (sail number 768). Normal single bridle, old mirror dinghy aluminium mast cut down to 3030 mm and using 3 mm spectra as stays. I fitted steel tubes in the bow holes to stop chafing the ply and large washers to spread the stay load. Bow doesn't flex more than a cm and the whole boat can be picked up by the pole. Prior to going spinnaker I did replace the decks (cracking ply) but that was just old age nothing to do with the spinnaker. I had the knots in the spectra stays let go but that's much better than breaking a bow. Must say Tim's advice in how to sail was more value in not stressing the boat. I'd check the condition of the hulls and decks forward of the main beam.