jockstraps

this halloween i am dressing up with my roommate and some friends as the us national double dutch team. our "uniform" includes very short shorts and i didn't own any appropriate underwear. so i stopped off and picked up a jockstrap. i don't think i've ever actually worn one before and when i put it on it didn't feel quite right. do the straps go under the buttocks or slightly on them? i tried it both ways - neither was comfortable. i think i need to get another pair of small undies.