So, I had this cute short sleeve sweater. . . Which is much too tight. This is why in the pic I chose to hold it up to me, rather than try it on. LoL.
First (no pic of this sorry), I put it over my girl, and pinched the sides together to get an idea of how much smaller it need to be. I pinched up a bit more than an inch on either side.
I laid the dress flat, inside out and sewed a seam down each arm as shown below (about
same as I had pinched together on her earlier)
Make sure if you do this that you round out the underarm, and cut the excess off as close to the seam under the arm as possible, so it lays right when turned back inside right.
Once sewn down both sides, trim excess close to seam, and turn inside right.
It was a hit! She loved the dress!