"Oh I get get it--you put the buttons closer together to get rid of the gap!" That's what most people say when I introduce them to Campbell & Kate shirts, but they're only seeing part of the story. Until I began designing the Campbell & Kate Signature Shirt, I didn't realize that there are two types of gap: the two-dimensional gap, and the three-dimensional gap.
Below is a classic example of the 2D gap. A 2D gap goes East/West or Left/Right, and it occurs when there isn't enough fabric for the bust. When there isn't enough fabric to cover a large bust, it doesn't matter how close together the buttons are. You're going to get a 2D gap--or, at the very least, 2D pulling.
That's why I love the current image on the Campbell & Kate shop page. My 32F model's pose almost always results in a 2D gap for women who wear a D cup or higher, but here there is none. We didn't use any photoshopping or pinning to reach this result. Neither did we put the model into a larger size. Her measurements call for an 8M shirt, and that is what she is wearing. There is simply enough fabric allocated for the bust.
A 3D gap, on the other hand, can be addressed with closer buttons. A 3D gap results when the top fabric panel--the one with the button holes--separates from the bottom panel to which the buttons are sewn. As you can see from the photos below, this is a universal issue for all women, not simply those with large busts.