I already had a size 38 DD, however the band was too big.
I choose a smaller band but a bigger cup 36DDD.
It was a perfect fit. Well as perfect as it can be.
Only a customize bra will be your perfect it.
No women as the same shape back or breast size or breast shape even.
I wish the cup was a little more full coverage in the front. However there is no side boo falling out.
Out of all the bras I have bought and there  have been many. This is the best on.
I do feel a difference with my back. Don't feel my breast hanging and therefore no pressure on my back.