User blog comment:B214/Volume 22 spoilers/@comment-29890029-20160913205138/@comment-9595671-20160914223457

The only characters we've really gotten that for are mostly the main characters from the ORC and Sona, and Vizor ironically.

In fact I think the last time we got any character's BWH sizes was... I'm not sure actually, I think it's been a year or two. You'd think Ishibumi would put more of them out.

I mean he does have the afterword of each volume, if he introduced a new female he could mention it there. At best we can only use comparisons via the anime and manga, and sometimes words from the light novels.

For one example, the way Azazel defined Gabriel's breasts makes me think not only are hers bigger than Akeno, but perhaps the biggest in the whole series. Though that's still a guess on my end and not a proven fact, so we honestly can't say for sure.