I actually have issues with the bottoms; I'm a petite girl, but my butt is the largest part of me due to my boobs being virtually nonexistent, and an XS is STILL too big for me at the usual stores. They hang off me like diapers. Tie-up bikinis are seriously saviors, like you said, but then you end up with a foot of string hanging off your thighs because you need to tie it so tightly :/