I would not sweat having to mount them on a stud. It might be "better" but probably not essential.
I use
E-Z Anchor products, especially the 30- or 50-lb self-drilling plastic drywall anchors. They are super easy to use, and your local Homeless Despot or Blowes should have them or something virtually identical. If you put 4 of these on each QS8 bracket, there is absolutely no way it will pull out of the drywall. Plus, when you move, you can unscrew them from the wall and fill the hole with spackle (unlike traditional "molly bolts").
It is very different if you are using the Full Metal Bracket, however. I'm talking about the flush-mount, T-bracket that comes with the QS8. Some physicist can explain the different kinds of force. I've got to go home and drink my beer now. And fix that girl a little toddy for her body.
That's how I have my QS8's on the wall. They are very solid. I don't worry at all.
