I also made a Fatmav-style GQ Zaku with red shoulders.
The "Zaku Fatmav [Overweight]" is one of the "Fatmav" squad members that participate in the Klava (clan battles) that appears in "Mobile Suit Gundam Sieg Axe."
I also made this using the regular Sieg Axe version of Zaku (GQ Zaku) rather than the Military and Police Zaku.
There were no major modifications, just painting the shoulder armor red and modifying the front of the Zaku machine gun as usual.
Like the "Overweight" with blue shoulder armor, I painted the entire thing with a light green brush stroke.

Zaku Fat Mav Spec [Overweight] (GQ) Style | GPO144's Gunpla works