I don't have much experience with extension work, but since it was a good opportunity, I decided to give it a try.
The fuselage frame was extended by about 5mm, and the waist armor and cockpit opening/closing section by about 4mm. After that, I used lacquer putty to some extent to treat the surface.
I had originally planned to modify it by mixing, but I decided to keep the mixing to a minimum and make use of the original kit.

1/100 Chaos Gundam body modification | さかな's Gunpla works