I could have sworn in one of Rhiannon's videos she says she (at her largest) was 5,500ccs - I think this may have been on one of Maury's talk show episodes.
If that's the case, then my guess is Minka would have to be at least that size if not slightly larger. There is a video Minka and Rhiannon did together recently where they are tit to tit and they are very similar in size.