Thank you.
That's a tall first step.
My buddy's rock sliders are welded just to the body. They wrap around and are welded the full length. They look great and are pretty stout, but when he landed hard on a few rocks, it pushed the entire assembly in. I definitely recommend tying to the frame to prevent that sort of thing from happening.
I wish I would have used 2x6 and pushed em out another inch. That might have saved me from a little rock rash right behind my door.