ohlavrac,
I have a pair of QS8s installed. I only used four of the six holes to mount mine. The two in highest and lowest holes the middle (one on top of the other) are in a stud. The other two holes (furthest left and right) are screwed into drywall using [ur=http://www.easyanchors.com/]plastic easy anchors[/url]. While the bracket itself isn't extremely stiff, the tabs that connect to the back of the QS8s are certainly up to the task.
As for the snugness back there, that's only really an issue if you're trying to use banana plugs. If that's what you're doing, consider going with bare wire, which won't make any difference in how your speakers sound.
