Gunsmithing Lightweight fill for Mcmillan stock mod

[Undrgrndprdcts]

I have a mcmillan stock with the old style adjustable cheekpiece that i dislike. Basically its a large aluminum block glued into the butt that the aluminum cheekpiece moves up and down in. I dont use it and use a light thin stock pack over top. What is a good light weight fill that is available, I'm thinking about milling the block out and filling the spot in. Machining/workmanship quality is a non-issue.

 

[Wannashootit]

West System epoxy with either the 407 Low-density, or 410 Microlight filler is my choice.
They do sell small "repair packs" of the epoxy itself so you don't need to buy larger quantities if you don't have any other use for it.

I've used West System for bedding as well, with High Density filler and powdered aluminum.