I’m interesting in finding a pattern or directions for a bi-swing (action) back for a jacket. These are often found in menswear or uniforms but seldom in womens jackets. I want to be able to raise my arms when I wear a jacket and a gusset would help, but I would like rules-of-thumb for creating that extra piece between the back and the sleeve. Sometimes this extra piece goes from the shoulder seam to just below the armhole and others go from the shoulder to a waistband (like a pleat). Any comments or suggestions would be greatly appreciated.