From what I've been able to research, Leia's vest is constructed in the same way as the vests the Endor troopers wear—even down to the waistband—although the lower pockets on the front aren't as obvious on hers. To figure out where to place a lot of the stitching details, I drew all over the muslin I made for the shirt, since I used the same Simplicity pattern (#9210) for the vest base. A good portion of that involved just standing in front of a mirror and eyeballing it.

When it came time to cut pieces out and assemble them, I used the normal shirt front, back, and facing pieces, just shortened a few inches all around. I also used modified front and back pieces for the detailing, and only the upper part of the sleeve pattern for the cap sleeves (I cut four, two as lining).

To put everything together, I first attached the back and the modified back together at the neckline and turned the modified piece out so that I had a finished neckline area. Then it was just a matter of ironing under the edge of the modified piece, sewing that in place, and adding the stitching lines to the right half. I then did the same thing for the upper portions of the vest front. Next came placing the two pockets at bottom after adding the stitching along the top edges. Once they were in the appropriate spots, I sewed down the facing as normal, then flipped it to the inside and sewed the wide seam down either side of the opening. The top edge of the facing got slip stitched down along the neckline. For the sleeve caps, I sewed the bottom edges of two pieces together and flipped them so the seam was sandwiched inside.

Once the extra pieces were together, the rest of the process was rather simple. Sew the shoulders together, making sure to catch the top of the front facing in the seam. Sew up the sides. Insert the sleeve caps to the armhole, and bind off the rest of the edge with bias tape. Add the waistband (two rectangles cut the length of my waist measurement, and approximately 2.5" wide, not including seam allowances). Because the hem of the shirt is bigger than my waist measurement, the vest is slightly gathered into the waistband—not a big issue, since it's seen on several of the troopers. I used two wide hook & eye closures to fasten the waistband together.