There are 4 firing drivers for the QSx speakers, one of which is on the bottom side.
Of course it is not "optimal" to have it covered up but if it is at least a bit above a bottom surface then at the most, you will have a fast sound reflection from the underlying plane.
Personally i think it makes the surround sound that much more dispersed but certainly i have noticed it taking anything away from how effectively the speakers make their surround sounds.
Like i said, get some little rubber 1" feet and just lift them off the shelf.
Until recently i actually had both my QS8s on shelves. Now one is wall mounted.
I will see if i still have a pic of the one QS8 sitting on its shelf.
Ok here it is:
