I don't consider myself an expert on the niche, but the one guy who I consider to be an expert runs two paysites: mature and chubby
As was said before, the older you get, the harder it is to maintain a thin/teen body, so I guess if you're out there for older ladies, you should be more inclined to accept a more full figure. Not necessarily all the way BBW, but chubby/plump for sure.