You will have to forgive me for the rough state of the patterns. They are working patterns, encompassing my thinking process as well as the changes that come from a fitting. I rarely have time to correct my patterns after the fact. I make the changes on the cloth and sometimes make a few notes if I can. I just don't have the time to redraw and cut out clean versions.
Anyway, we made two jackets for this individual. One was a black barathea cutaway coat and the other was the fine grey beige striped wool. On the top you can see the the back pattern for a black cutaway coat and on the bottom the changes I made to the pattern for the striped wool.
Men's jackets generally have a hidden dart in the shoulder seam.
This means the back shoulder is longer than the front shoulder. The jacket must be big enough to go over the prominence of the blade. Above the blade, you then have excess fabric that need to be handled somehow. What do you do with it? Well, usually some of it is taken care of by easing it into the shoulder seam. Some goes into the armhole where it could also be eased a bit or filled by shoulder padding.
The amount of ease depends on the figure, the style of the jacket, and the particular fabric you are using.
In this particular case, I was dealing with quite a stooped figure, and rounded blade and shoulders. The period (Edwardian) didn't call for large shoulder pads, so I had a larger amount of fabric to get rid of over the blade in addition to the stooped back.
In the top picture, for the cutaway coat, you can see that I transferred some of the excess shoulder ease into the curved frock seam, and since the fabric was plain black, I could keep the curved centre back seam and no one would notice.
In the bottom picture, which was for the striped fabric, I made changes to the pattern to straighten the CB seam, and in doing so created even more ease in the back shoulder seam, which had to be turned into a dart.
This dart was placed alongside a major stripe and is much less noticeable than the bulls eye effect that would have happened down the centre back seam if I left it like the pattern for the cutaway. I did gain a bit of extra length over the blade in this manipulation, but it seemed as though that particular fabric needed it.