The bottom deck is 3mm Okoume ply from Midwest Boat Appeal in St. Bonifacius. If you have never been there, it is definitely a great boating resource. They stock about 10 different marine plywoods, Sitka Spruce, and Mahogany. I asked why they have Sitka, and it is basically for the hydroplane and homebuilt aircraft guys. Now on to mounting hull hardware and steering.