It will work and don't worry about the 9' wall. Just hang it so the bottom of it aligns with the part of the lamp where the foot and slender piece connect - maybe 4-5" off the buffet I'd say. My main concern with mirrors is whether or not they will reflect anything beautiful or interesting. Is there a view through the window or will it reflect the chandelier? If so, those might qualify to merit reflection. Remember, a mirror really doubles what is reflected, so it should be something you like well enough to see twice!