>>279718116
>>279636999
Mai's canon measurements are B89/W58/H86 (which is roughly a C cup if I recall), but I do tend to make her chest a little bigger in SDT.
I wouldn't want Ilulu level (although I do like her) though, it wouldn't really fit her.
Picrel's the peak and probably biggest I'd be comfortable with if you want to do large breasts.