Howdy!
For my build I went with 2" below the shoulder seam for the patch. On this real military garment, the armscye is off the shoulder, while in the references it's drawn at the top of the shoulder. This puts the patch visually in the correct place on my arm as a whole, IMO. I will also move the buckles closer to the pistol belt as seen in the one reference.
I will take new reference pics with the loose harness strap behind (full body pics and detail pic). It may take me a weekend or two.