I have a strength of materials/safety margin question on my back seat project. I need to build a modular rear seat mount that will hold a pair of cheap Summit polly seats with 5 points. This thing will be completely self contained and bolt into the cage only when I need to carry 4 rather than 2 (wife and daughter, or friends of me or my son). These seats will not be occupied on the “we’re probably going to go over” stuff, but need to be safe in the “oh [I love Jeeps], I didn’t think that would happen” case. The roll cage is no problem, but the seats have to stay low so there is not much leg drop. Sorry for the sad pic, and an isso view would help, but this should work without having to do CAD… It will be attached with wrap around clam shell clamps at 4 points on the end of the red bars (see pic). These will suspend the seats between 2 parallel bars about 42” wide. The seats almost touch in the center, closer than the pic indicates. The goldish side bars are angled down sharply to allow entry from the sides. The horizontal shoulder bar will mount the 5 point shoulder harness. The brown center bar is the main brace for the shoulder bar and provides a good handle for the occupants. Here is the question: What is the minimal reasonable material to build this thing out of? I’ve got round stock in 1” x 0.120” and 1.75” x 0.120” as well as square stock in 1.5 x 0.188 on hand. I am usually accused of dramatically overbuilding things, so my first impression is to use the rollbar material, 1.75 round. I *think* it will be ok, but sort of border line, to build the whole thing out of 1” round. But I don’t know. This is something that I want to keep as light as safety allows (without exotic materials) because I expect it will be added/removed frequently. It takes the place of a toolbox that will normally mount in that space (more gear for longer/tougher trips than when the rear seat is occupied). Smaller tool/part boxes remain even with the seats. So, what do you say?