I have welded quite a few stands myself, ladders and hang-ons, all out of steel. They are very solid, if heavy, but do not have any fear trusting the life of me or my sons to them. I do not use climbers and have never attempted one, they don't fit our MO.

Welding aluminum is very different from welding steel, we do both at the plant I am production mamager at. Steel is easy, aluminum is tricky. If you are planning on trusting your life to it I would really reccommend getting someone to weld it for you. I'm not saying you can't do it, because I don't know you or your skills personally. I'm just saying don't take it lightly and do quite a bit of weld testing before you do it for real. I wouldn't trust my welds on light wall aluminum 30 feet in the air, and I have welded a fair bit of it. Aluminum also work hardens and stress cracks, which is something your design will have to take into consideration as far as where it flexes.

Be careful and safe. Good luck.