Finding a sports bra for larger boobs is a tremendous task. At the time of buying, was wearing a 36-38J, but found all other brands and styles to fit very very small. Thinking this was universal to all sports bras, I bought this in a 38J and 36J online for in store collection- half anticipating both to be much too small. The cups were, and I ended up purchasing in a 38JJ. Few weeks of going to the gym, however, and my back size had decreased and the back had stretched, seriously reducing its effectiveness. Went to store again four months later and bought in the Black in a 36K - a size I never thought I'd be. Compared to other 'normal' styles I've bought, I'd suggest sticking to normal backsize and going up a cup size.
Better than many other sports bras (it does go on, after all), but don't expect miracles - I still hold my boobs with an arm underneath as I run. Not sure anything can stop the bounce