Flat/protruding abdomen alteration: theories on what it is and isn't

I have more than my share of fitting books, and I've seen several variants of flat/protruding abdomen alterations. In general, the protruding/large abdomen alterations add width and usually length over the abdomen, increasing the waist dart intake as well. The flat abdomen alterations do the reverse.

Now, I certainly don't have a flat stomach, so it had been in the back of my mind that I might benefit from the large abdomen alteration—that is, if I ever got around to bothering to do it. But on the other hand, I've often felt that skirt and pants patterns (and to a slightly lesser extent, RTW) feel too high in the waist in front, especially compared to the back. Besides, I often need more waist shaping in the back, not the front. So I couldn't quite square the two.

Since I've looked into it further, here's what I think: the usual large abdomen alterations work best when the front waist is small and indented in comparison. So the largeness has to be over and done with somewhere below the waist. As somewhat exaggerated examples, look at this Toulmouche painting or this Annie Oakley poster. In both cases the waist is quite small (due to the shape of corset worn at the time), and there would need to be quite a bit of front waist shaping to mold the skirt from the roundness at abdomen/hip level up into the narrowness of the waist. The same goes for Christian Dior's Bar suit, with its fitted waist and padded hips. Generally, the large abdomen alteration methods presuppose your pattern has the correct waist measurement already, and you just need more length and width further down—wider darts then take up all the excess at the waist.

But what happens if you have a large front waist too, or you have a posture that shifts your upper torso a bit more forward relative to your hips? Counter-intuitively, that might actually need a flat abdomen alteration, as it will result in less dart shaping at the waist. The problem is, most of the methods for those will decrease the front hip circumference as well, something you might not need unless you've started with a larger size than your hip measurement would call for. What some people do is simply leave any front darts unsewn, or sew them narrower (and maybe sew the back darts wider to compensate, if more shaping is needed there instead). The front waist may well need to be dropped too: if there's less of a curve then there's less need for length—though extra length may be needed for apple shapes.

Anyway, I'm currently applying this theory to a jeans pattern I'm working on. I've erred on the small side when choosing a size, shortened the rise length to get it shorter in front, and done a large derriere alteration to make the pattern proportionally bigger in back. I did add a dart in back, which isn't usual for jeans (normally that shaping's moved entirely into the back yoke) but I think it might look interesting; the tips will be hidden under the pockets. And I realized after all this that my fabric had stretch, something I'd forgotten about. We'll see how that goes.