I have 2 1/4" space under a rack on my Jeep. I want to carry a flat ladder under there. It will be 60" long/high with both sides and steps out of square aluminum tubing .125" thick. I prefer the steps being 18" wide but 16" will do. The man stepping on the ladder weighs 250 lbs but he may have 50 lbs of gear and clothing on him. The ladder must be no thicker than the stock it's made of. Can I use 1 1/2" square tubing? If that's questionable, I can use 1 1/2" x 2" or 2" square. However, the latter two add weight I'd rather not lift.
Jerry
You're asking an on-line forum with sources you don't know for a design that could result in significant human injury if it fails. Are sure you want to do that? I would suggest that you at least sketch up your own design, apply the standard deflection equations found elsewhere on this forum, and then run any questions by the members.