I am 36c, but also have dropped since triathloning, but definitly wear a heavy duty sports bra underneath, a synthetic brand that dries out as best as it can during the rest of the race. It also keeps the trisuit from being "transparent" in the meshy areas. Bestform (Target, Walmart, 9.99) . A good friend of mine who is large, wears TWO bras under her trisuit. I do have trouble with chafing in the center during regular workouts, especially in the gym where I really sweat, so now I put a dry washcloth folded up right in the middle of my breasts and under the bottom elastic, and change it when it soaks through. In races, well I just chafe, very uncomfortable and red for days after.