There's really no comparison between the two versions, but the most significant thing to take note of is that almost all of the new support comes from a significant reduction in the width of the back panels. Secondary to that is the bust "pocket" created in the side, eased into that straight line on the back side, under the armpit.
I can also now appreciate why the straight front seam was never quite the correct choice for me, given that my bust and my belly fall at different widths here, and my belly wins out rather noticeably. I'm going to blame that on my love of donuts.
So that's all I have today, but I thought some of you might be curious about this as well, so there you have it.
I have decided to move forward with the linen I have on hand, rather than getting a sturdier material. I've taken a look at how the pattern material strained with the tightness, and I believe that the linen can handle it. I'm sure I'll want to make a second chemise soon, so I'll save the sturdier material for that.