I made the dress via this 'ible and thought it would be cute with a little shrug.
I put on the shirt, pinned the spot where I wanted the length to be, took it off and cut it. The shirt has a little piece of ribbon in place of a tag in the back, so I used that as the center mark to make the first cut up the front. At this point my cuts were rough - semi straight but not tidy enough.
Next I laid it out and folded it with the two front pieces lined up and trimmed them straight to each other. I the, folded it so that the bottom lined up and did the same. I re-laid the front lining up and cut the collar trim at an angle and curved the bottom.
To further tidy the edges I set my sewing machine up to do a "serge" overcasting stitch and went from the seam for the collar trim on one side all the way around to the seam for the collar trim on the other. I like that it helps cover any slight imperfections in the cut and gives a cute little "ruffle" to the edges.
I had some ribbon trim left over from another project so I cut 2 7.5" pieces, cut one end of each piece to a point and folded the other end of each piece over roughly 1/4". I lined up the folded over edge to the edge of the front piece, over the seam for the collar and sewed it roughly in line with the overcast stitching so it sort of looks like it was all done at once.
Anyway. Here it is with the dress and a shirt I will wear with the dress :)