Anima: The bottoms are trained with "u-ring bikini bottoms" so include that to stabilize the classic look.
I think this was a meme swimsuit for a bit. It's a bit jank but works often enough for me.
For V2(and maybe V1) adding "side-tie_bikini" to the negatives should help with generating the bikini bottoms with the U-shaped piece of metal.
FYI This dataset contains zero men so if it works for men, great but I have not and will not test for it.
Side note: I do take informal requests(basically a bounty that you don't have to pony up buzz for) if I like the idea(Tips are nice but not required since if it's a good idea then I'll get generation Buzz). Just leave a comment on one of my models or DM me. (Comments are preferred since that let's other people see that I'm actually fulfilling informal requests.) DMs are perfectly acceptable if your request is a bit out there and needs some image examples or something.