Do you have an attic?
You could always run a 2X4 between the joists in the attic, then mount the QS8's into the 2x4.
Similar to bridgeman's idea but have the wood in the attic instead of on the ceiling.
If you do this I would make sure that you drill into the 2" side of the wood (so the screw has 4" of wood to 'bite' into.) Not to mention the reduced deflection and higher moment of inertia when the 2x4 is bent about that axis.
The tricky part would be placing the wood exactly where you want the speaker... you could poke a hole up from the ceiling and stick a wire hanger through to see where to place the 2x4 in the attic.
bridgeman,
Here is the link to the omnimount page:
http://www.omnimount.com/consumer/product.aspx?ProductId=fe7fa0e3-d6f7-4b54-885d-34db03c2f7e1The 'installation instructions' pdf talks about drywall installation, but it shows a picture of a wall at the part so I do not know if drywall ceiling mounting is ok.
On a side note, My audio pier is made by omnimount, here is the picture:
It is a VERY sturdy piece of furniture.
It says it is rated at 50 lb per shelf, but It definitely feels sturdy enough to support someone standing on it.
