I've had two civvy girlfriends who were enormous up top, both of them in their 40s at the time, as it was after my divorce. Not sure of the cup size but defo in the Js or Ks, and couldn't get bras in the ordinary shops.
The thing I found fascinating about one of them was how firm hers were. At one point I thought they were artificial, as they were that solid, but they were in fact natural. The other lass's felt as you'd have expected.
What makes some ultra firm I wonder?