Stan, you didn't provide a key measurement: how far behind the listening position is the back wall? In a 5.1 setup the side surround speakers should generally be placed on the side walls a little(maybe 2-3')farther back than directly to the side, to lend a little "phantom" back effect in the absence of 7.1 back speakers. If the back wall is close to the listening position(say not more than about 3')then putting the QSs on the back wall widely spread almost to the side walls is very little different from a side wall mounting almost at the back wall.
