This is a lively group. I love it. Anyway, thanks Mick for the advice and thanks Matt for that PDF,that fit the bill perfect. I think this can be the offical end of this thread....see you in the builder forum.
Hopefully no one reads that first post and suggests I put a large diameter hole in the center swearing it will still float....

Off to desperately search for a plywood source. I am near Pittsburgh, PA in the US if anyone happens to read that knows of a source nearby.