Guy's it's not quite as neat as you can't can't see behind the camera
Doc, You can't see to well in the pic, but first I raised the legs on doubled up 2x4's, and lengthen them, and there is a piece of 1/2" plywood screwed to the back to make it more rigid, and then I screwed it to the wall studs. It really firmed it up for me.
Roamer, Here's the pic's I rescued this from the scrap heap, as it was found when some one dumped it in the woods, and we were doing forest cleanup. I think it was originally a grinder stand. If I were to build one, I would use a light truck rim, leave a tire on it, then fill the tire, and rim with concrete to make the base heavier.
I set the stan on some MDF, and then screwed thru the carpet to the subfloor. Don't worry guys, I'm a widower now, though I still hear her talking to me,
that's why I vacuum regular, and I'm replacing the carpet in the Spring.