I'm pretty tiny, and I got the smallest size which I had to squish *all* the way down for my back and waist, which totally sucked and took me months of procrastination. but my hips and butt are normal sized, which wound up being bigger than the size small. so I stuffed that with batting, which works reasonably well, since that's not an area that gets squished in any of the clothing I make.

in summary? I'd recommend you go smaller because it's easier to pad up than squish down.