I bought a free standing bag stand for my basement, since hanging it from the floor joists shook the house. I learned two things: first, make sure you kick it head on--any motion toward the supporting rods can bend them if you kick it hard enough; and second, keep the bolts tight, since again, any play can result in it breaking or collapsing on you.
I got the perfect solution If you got the bucks Go to balazsboxing.com and buy their freestanding one station. you can even get a chining attachment. I live on the ninth floor of a building in Chicago and when i slam my 135 pound Thai bag nothing vibrates or shakes.