Floor Standing speakers and height

I use four floor standing speakers in my HT. They are all about 40 inches tall. I also use a couple of regular recliner type chairs that have taller then head, high backs. I was wondering if I might be able to get more detail from the rear channels if I were to elevate them about 6 or so inches. Has anyone every experimented with this?

seems like i remember reading somewhere,that it was recommended surrounds be elevated 6 to 8 inches above the mains,although don't quote me.

http://www.audioholics.com/techtips/setup/loudspeakers/hometheaterspeakerlayout.php

ok this says ABOVE ear level...2ft...

doesn't help much with floorstanders
but maybe you can dig around the site.