Alex, the surrounds in a 5.1 setup should be placed a little(maybe 2')farther back than the listening position, to help lend a little more back surround effect in the absence of back speakers. Since they're still side surrounds they should be separated as much as possible, almost to the side walls, although they're ceiling mounted. From your description, being at the sides(again though, farther back than directly to the sides)might sound a bit better.

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Enjoy the music, not the equipment.