Well people, I've finished my cat box. It turn out great. All the parts and materials cost about $60. I made it 12' x 22" w x 12"t. It's totally corrosion proof and should be weather proof. I had to make it long to fit the bowsprit pole. I ended up using Polyethylene barrels. You know, The big 55 gal. blue or white ones. I split them in two, cut the ends off, then sleeved them together and rivoted. I used 3.5 barrels to get 12'. the forward end is intact, and I put a hatch on top. The aft end opens for a door like a reg catbox. All this is screwed to treated plywood. Hope this gives other ideas for box projects.