Sail, Dacron, Pentax, Kelvar, Mylar whatever, but no square top, if you won't build the boat because you don't think its modern enough, maybe choose a another class. I don't think they'll bend the rules to suit for that reason.

Marine Plywood, Gaboon if you find some good stuff.

Quantity, guessing 7 sheets, 1 sheet of 50mm foam.

Fittings, Masts etc... Goodall Yacht Sails, the Association or a Boat Shop.