My dd is 5.5 months, and 13 pounds. She's quite short and chubby. She has rolls on her thighs and lately I've noticed that her FB, especially when stuffed a lot for night, can leave some pretty serious red marks on her thighs. However, on the waist snaps, we still have room. Since medium FB's say they start at 13 pounds, and smalls are supposed to go up to 16 pounds, will mediums be humongous on her? If I loosen the waist snaps will that make any difference on the fit in the thigh?