odd question about stand-mount speakers

Is there any reason you shouldn't turn stand-mount speakers upside down and listen to them that way, as long as you use some kind of vibration control/decoupler between the speakers and the surface they're placed on? The reason I ask is because, at least in a near-field setup, I would think having the mid/woofer ABOVE the tweeter would enhance image height/size -- assuming the tweeter is kept at ear level. (A couple of asides: I don't currently have bookshelf speakers, otherwise I would experiment. Will likely be buying some in the near future though. Also, I know that there are some stand-mount speakers that place the mid/woofer above the tweeter, but the vast majority do not -- most of the ones I'm interested in do not.)