ohh thats the same one i have! though i ordered it online. it's great. i got the mini (3.5'') and feel its a good size for me, and i'm 5'6'' 150 lbs. i suppose i cant say too much since i havent tried the small, and who knows that might 'suit' me better. but i am totally comfortable with the mini size with me and im a bit bigger than you. im not exactly too caring about having a big thing so to say, but i def don't want a small one either haha, so that might say something too.
anyways just figured id throw my two cents in =P