Hi! I’m making a jacket for someone. Everything fits ok, except the back seems too narrow. When she extends her arms in front of her, there is strain on the part from one armpit seam to the other. The back of the jacket is princess line style. I had to adapt it at first to make it fit her back, but I guess I took it in too much. How do I make it a bit wider and still fit her back’s shape? Thanks!