In drafting by proportionate it's made 1/3 scale plus 2 1/4. But if back has a 3/8 seam only on the sideseam, creating and excess 3/8". So if the back only has one seam in the side, wouldn't the width be 1/3 scale plus 1 7/8? Or is the extra 3/8" for shaping the back, or for an excess drape? I'm just a little confused because the width of back was usally made 1/3 scale plus 1 3/4 (for a 1/4" seam in the side), or 2" (for a 1/4 seam in both side and back).