Aha, okay. So the front and back, which are not going to change shape much other than to make a lumpy bit flatter, have flat boning. And the spiral is on the sides so that it doesn't dig in where it's trying to tuck stuff in. Got it. Understanding that concept suddenly makes this seem a lot more do-able.
I want to add some boning channels to the buckled belt/faux-corset from this pattern
, so that it won't wrinkle and so that it could hold my belly in a bit flatter, but I'm not going to go for waist size with it. I think it's meant as a men's girdle so I'll probably have to make it wider vertically.