Roland,

Go to this site: [Link: dolby.com]

Yup, you guessed it. It's the official Dolby site, creator of Dolby Digital. They have suggestions for speaker placement (for surround, 2-3 ft above the listener ear, with the listener sitting down).

From my experience, if you can't mount it on the wall, then mount it IN the wall, since surround speakers are for creating soundfields, not imaging.

Good Luck...