That looks pretty cool. Like Duckman said, he looks kinda buff.
I also was modding an action figure to be look like a Vault Dweller... But the figure I chose as the base turned out to be a total crap. It was some garage guy in a jumpsuit from the 80s and I took it from my parents' house during Christmas time. (I accidently carved a hole into his stomach with a knife...) I'm in a search of better base figure now. One that can take modding better.
I'm also planning to use paint and green stuff.
I'll post pics of the progress when something is happening.