When I wrote it, long before the appearance of the Full Metal Ceiling Bracket, it was a conservative suggestion. I just didn't want customers forgetting about the top-firing woofer and jamming the QS8 or QS4 up next to the ceiling.
In fact, the QS8/QS4s are really forgiving of virtually any crazy placement. Certainly 4 or 5 inches is sufficient for the upward-firing woofer to benefit from the ceiling reflections.
Would the surround soundfield benefit more from greater placement away from the ceiling? Maybe, because there will be a greater number of reflections from different parts of the ceiling and other surfaces if the upper driver is farther away. But when I move my own QS8s into different positions, I have trouble hearing any significant differences.
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