excellent job on this instructable and the actual project. Congratulations on winning the grand prize!
sorry if you mentioned this but what are the holes in the top for? The oblong holes along the sides I assume are to create storage areas and cut down on weight? My only concern would be the weight of this thing. It could be redesigned to be the same size but in two pieces. I like the design but I would probably make my own a bit longer and in two pieces that you just clamp together or something.
The Ultimate Kid's Treehouse