I did a quick CAD drawing of what a steel frame might look like for our dimensions. I used 1x1 and 1x2 steel tube (with a little bit of cnc work on the curve section and a little bit of pipe). I have arranged things such that 2 inch R5 foam can be installed everywhere and there will be no place inside where there is not at least 1 inch of foam between the steel and the inner wall. This should help with thermal isolation.
Most of the steel is 0.065 gauge but I used 0.120 for the corner vertical 1x2
The total weight as drawn is 580.8 lbs
3749" of 1x1 1/16" 258.3 lbs
2067" of 1x2 1/16" 218.7 lbs
426" of 1x2 1/8" 80 lbs
197.25" of 1" round 1/8" 18.5 lbs
75" of 2" wide 1/8" plate 5.3 lbs
