I used a normal asa fitting and drilled and treaded to holes then Epoxyed it together. if you just drill a hole then tighten the hell out of it when theres Epoxy on it, its not coming off.
if you want some help on the design just write me.
and yes it dose go under my mask.
heres my stock:
you should see it with my friends grenade launcher and a red dot or scope on it...My poor back.