Weight to size ratio can be so different, can't it!? ;)
I remember I worked with 2 girls, one was about 5' 7", size 6, and the other was about 5' 2" or so, size 4, and the 5' 2" girl weighed a couple pounds more than the 5' 7" girl!
It was all about muscle though. The 5' 2" girl definitely...