Easing the shoulder in tailoring
When I drafted my pattern, I cut the back shoulder about 0.5cm longer than my front shoulder. The idea is to do a large running stitch on the back shoulder and pull it slightly to ease it in, before carefully pinning the the two panels together. If the back is still too big, it is fine to continue to ease it in.
The idea is so the back has a slight raise or role too it, to make the area fuller to slightly role. It is very rare that you would see good tailoring that wouldn’t have this done to it. Obviously, 0.5cm is what I did for this make and have done previously, but if added fullness is require then increase the amount slightly.
I also did a slight kick on the shoulder towards the sleeve head of about 2cm in total to allow my shoulder pads to go in.