Nicely done, John! I'd been using a wooden step stool I made at summer camp when I was probably 10 years old. It finally gave up the ghost and I was looking for a replacement and I think you've given me an idea.
I don't know how to weld so I'm collecting welding projects to practice on (sometime). I'm planning on a gas strut prop system. I'm thinking I'll do something like what you have but fabricate stands where you use your jack stands.