I would have to agree that Spanx sizing is a little off. I still have the ones I bought when I was 25 lbs heavier and they fit me much better now and are still plenty slimming.
I wore them before I lost weight but found them very pinching and they did roll. I would buy the next larger size if I were close to they top of a range. It still does its trick and looks like it is made for a small child, and you're supposed to squeeze into it.
Now that I'm near the bottom of the range, they fit great.
