The Merits of a Basic Fitting Pattern
If you were using the sloper that this pattern was drafted from instead of your own, of course, there'd be no such questions. You'd see exactly the amount of design ease the designer intended at every seam, and how (and where) he or she had repositioned the dart shaping that's built into every sloper for the female figure. The exact relationship between the outlines of the sloper and pattern at every point is the record of the designer's idea of a good fit for that garment.
From this relationship comes the idea that it makes sense to alter a pattern company's basic fitting shell before trying to alter individual patterns from it. If a company's patterns were all drafted from the same sloper, once you knew how to make that sloper fit you, you'd be able to change any other of the company's patterns and it would fit you the same way it fit the sloper. Well, this implies that you should adjust the basic fitting pattern from every company whose patterns you want to make. But not all companies publish one. Worse, not all patterns from companies that do publish one are drafted from that same sloper, and there's no way to tell which aren't! Happily, there's a simpler way.
Introducing "Match the Slopers"
To make the process I'll describe easier to visualize, start by imagining an ideal world in which every pattern comes with an outline of the sloper it evolved from drawn right on the pattern, aligned at center back and shoulders as described in the "2-D dress-form" example above. Next, imagine laying your own sloper over the "ideal" one, also aligned at center back and shoulders.
Now, what if you simply cut apart the pattern and shifted the pieces so the outline of its sloper exactly matched yours? You'd have altered the pattern to fit your sloper, without changing the design ease the unaltered pattern had to start with.
I've actually traced an "ideal" sloper onto a commercial pattern derived from it (see Step 2 below). It turns out that with nothing more than a few horizontal and vertical tucks and/or slashes, it's easy to make one sloper's outline match the other's. Once I did it, the resulting garment fit!