Before sewing in the shoulder pads I secured the canvas interfacing to the arm hole seam allowance. Up to this point it's just been flopping around at the shoulder.
The shoulder pad is then aligned with the edge of the armscye seam allowance and pad stitched to the canvas. I have to slide my hand in between the canvas and the coat fabric to keep from catching the coat fabric with these stitches. If the fabric gets caught it will create an unsightly dimple on the outside of the coat.
Here is the completed pad stitched shoulder pad. There is no canvas on the back of the coat so the pad is basted into the arm hole seam allowance. If the shoulder pad projects past the seam allowance it should be trimmed back.