For my hull (No Captain Nemo I haven't purchased and I'm not welding this material together yet), A36 5/16" thick 30" x 144" with supports (3" wide x 1/2" thick) every 18 inches, I calculated that its crush pressure/depth would be: 1294 PSI, 2905 Feet and I could operate it at 1000 ft no problem, do you all agree with this, if not, why, if yes, why? Thanks, Graham Kuberski