There's this old T&A chart that groups the umas in ascending order of... "asset size". Notably, it's adjusted for their heights and waist sizes (as an approximation of "band size"). 2nd image is the one for hips.
It's from 2021 though, so it doesn't have most of the newer characters.
Anyway, other than Windy and Grass at the "thiccest" end, there are also Helios (156cm B82 W53 H85) and Bourbon (160cm B86 W54 H87).