Hi Dave, you are undertanding perfectly The top of the frame comes away from the wall. I think this was primarily due to the hanging chain being about 1/2" - 3/4" inch away from the wall, as well as my hanging wire (i.e., the one that goes across the width of the frame) being too long. In addition to tightening up the hanging wire I'll also add small rubber bumpers to the bottom corners of the frame as you suggest.

Thanks to all for the helpful thoughts on this....