Body wise it is a great fit. Your discomfort after zipping up probably comes from the small armhole. Even a trimmed Aero or Eastman with say the same chest measurement as your RM will likely still has wider arm and armhole.
I think you’re absolutely right. It is the high armhole that’s brings the shoulder closer when i zip up. It’s the same feeling i had when i first got my Board Racer, although it now has relaxed quite a bit. This A2 is actually a lot more comfy than how the BR was.