Question about scroll frames

Hi --

I generally use Q-Snaps to hold my work, and I'd had no major problems. I have a question about scrolls, though. Do the scrolls hold one's work taut enough all the way around to allow for easy stitching? That's one really nice thing about Q-Snaps: if the piece gets a little loose, one simply gives one of the snaps a partial twist. All better! From what I've seen of scrolls, it looks like the two edges perpendicular to the scroll bars might get a bit saggy or floppy. And how does one keep the scroll from loosening --- does it have some sort of clamping system to prevent unwanted unrolling?

Thanks!
--Danny