While looking through the photos of the concrete sub, the schematic/sketch showing the concept with the diver lockout and utilizing three chambers caught my eye. That looks to me like a nice idea for a larger steel sub that could be done by a home builder. The three separate chambers would have some benefits that a single hulled craft wouldn't. Primarily, the strength of using spheres bolted together with big strong flanges, and the ability to isolate sections from one another should the need arise. The space between the pressure spheres and the streamlined outside would allow lots of design work for MBT's and such, keeping the sub very sleek. Got me thinking with that one. Frank D.