Mounting them on the wall, near the ceiling, angled down will work fine as long as the top woofer has room to breath. You can also hang them from the ceiling with a DIY bracket or one of Axioms new ceiling mounted brackets which are a little spendy.
If your saying flat on the ceiling, I would not recommend that as the tweeters will be aimed down at the floor which would be going against the purpose of surround and interaction with the other surround speaker on the opposite side of the room.
You want bullits and helicopters to sound like they are moving from one side of the room, through you, to the other, this would not be the case if you mount them flat on the ceiling.
The Q's are not that big from front to back, maybe a few inches more than the W's.
I don't want to make your wife mad, lord knows I had a lot of talking to do to talk my wife into what I did, but now she understands.
Here is a pick of how I mounted my surrounds with cheap Menards shelf brackets. These are my old Mansfield Beech Qs8's, I now have black ones. My website has many pictures if you want to check them out.
one with my black Qs8
