I’m taking my time on this coat. I decided to interface the upper backs on the bias with horsehair. I chose not to add front and back shields based on the fit. There isn’t any caving through the shoulders. I wanted the bias interfacing through the back to keep the movement of the tweed fluid.I underlined the back with polycotton broadcloth. The hem is interfaced with bias strips of horsehair. The seam allowances are all catch stitched into place, although these pics were taken prior to that step. Here’s the back with all the pleats.