For people who have ordered skirts from www.runningskirts.com, how do you find the sizing? I'm debating between the 4-6 size and the size 8. My waist fits perfect in 4-6 size jeans but my booty is still on the 8 . I wear a size Medium in most work out clothes. I just don't want to get one and it's too small where it rides up or that it's too big and falling off of me (both would be equally great race photo's ). What do you suggest? Do the sizes run true? TIA!