The suit is very cute. According to the underbust/waist/hips measurements provided, however, it should not have fit me even in the biggest size available. I went ahead and ordered my usual (XL/16) and it fit well. The only downside is that the torso is quite short. I do have to tug this suit up in order to cover my nipples.
I purchased an XXL to test for myself. Unfortunately, the only difference between an XL and an XXL is the width. The length was exactly the same. I am keeping both XXL and keeping the XL. I'll just have to be extra careful that I don't flash anyone.
Honestly, if this suit weren't so cute I'd return it and not bother with trying to modify it or constantly tug it up over my breasts, but the color and style are lovely on me and I normally hate how I look in bathing suits.