I also need to figure out how to solve a problem I have with patterns – I tend to have some excess fabric at the nape of my neck. My shoulders aren't the issue, the measurements for the shoulder seam fit me just fine. I just tend to have some extra fabric right there at the neck and going down a few inches. This is a fit issue I've had all my life in ready-to-wear clothing. The shirt I pulled together last week, the one I labeled not a success? I did a bit of tapering right there and removed some fabric, which worked pretty well. That the shirt didn’t work was entirely due to using fabric unsuitable to the construction of the shirt – call it user error!
Anyway, I need to read up on how to alter my patterns for this fit issue. God knows there are all sorts of tutorials out there on things like full/small bust adjustments, prominent shoulder blades adjustments etc, etc, etc. I just haven’t seen anyone talk about this and honestly I don’t even know what to call it. Gapitis at the neck? Pretty sure I’m not the only one in all of sewing history to have this issue.
Edited to add: