Here is the offending baggy back as sewn, and next to it, the same back unsewn! My sister laughed: "You tease... You make me a jacket, then come visit me and rip it to shreds!"
Predictably, the problem is in the side panel, same as in the raglan shirt pattern. I make the triangular tuck and pin the seam in place, thus shortening the back.
But where does the excess back length go? It spills out the top of the seam, into the shoulder/armscye!
I make grumbly remarks about my sister's body, and she says I'm giving her a complex. Then I pin some more, and she pretends I'm stabbing her ("ow, my flesh"). I angle this seam so it goes downward into the vertical seam and doesn't change the shape of the armscye, because I want to avoid the extreme hassle of altering the sleeves as well.
Eventually, it's all pinned out... and a peculiar bunch of seams we now have! I baste them down and prepare to sew: first the back chevron, then the vertical seams, then the sleeves into armscyes. A little hand-sewing is required around Center Back, but not much.
I say we call those chevron seams a design feature! I wish the vertical lines of piping flared out at the bottom instead of the top... I think this was the wrong pattern to start with. But I don't hate it now, so that's good!
Quilting, dressmaking, and history plied with the needle...
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