DS is almost 8 months old, and Hanna size 70s currently fit him very nicely length-wise (maybe a little bit big, but not much). They are still very big around the waist. He is quite the little stringbean, so when I'm buying ahead for next summer, would you suggest 80s or 90s? I'm somewhat concerned that the Hanna 80s will be too short, but I'm even more concerned that the size 90 pants will fall off his skinny little fanny! Obviously, every baby is different, but what size Hannas are your 18-24 month little ones wearing? Thanks!