I'm going to try adding stuffing to square off the shoulders, I think that's the big factor in his body mass appearance.
If you look at the real photo and the PF's neck, the PF looks great, right size, shape and all, yet somehow where it meets the shoulders is off, so where the jacket collar falls relative to the neck and the shoulder size looks a bit off. It's almost like the body was made by someone while the head another person and then slapped together and it's a slight mismatch.