I tried on the shearing-lined HJ at Barneys NYC yesterday in my usual Eidos size (50). It is cut pretty trim to the body. I was wearing a button-down shirt at the time, and I don't think I could wear more than a medium-weight sweater on top. I wouldn't want to size up, because the arms would be way too long. Antonio can say more, but perhaps this was designer's intent? After all, one generally doesn't go hunting in the dead of winter.