just thought i'd add about the timber i'm using. paulownia is about the best, light - almost as light as balsa, waterproof, very strong by weight. but expensive and hard to find. i found a stand of old japanese cedar (cryptomeria japonica) growing on the farm which where planted in the early days of exotic timber trees trialed around new zealand. its very light, quite durable and waterproof. hey they've been making buildings out of it in japan for a few thousand years. best of all it was free. $450 got it all slabbed up (2 trees) and i then mill it in a mates joinery factory, not as easy to work as paulownia, but i do like the grain, this board is sheathed in flat sawn boards and the next one is using quarter sawn. it will be interesting to see the difference