I wear fitflop all the time, only shoes that help my knee and back pain. I ordered these in an 8, since I had printed the fitflop sizing chart from another site, which had me at an 8. Way too small, ordered a 9 and they are perfect. Spent all day on cement floors today and still felt as if I were walking on a cloud. Now if I can get the tall ones in my size, I will get them!
I would suggest printing the chart, then going up one full size from whatever it says.