Mike that's why I saved that one, I was thinking about taking an FFF bolt and making a vent liner out of it, just have not got around to it yet. It really makes sense, and yes they are hardened but not any harder than a D hard bolt an F would be an up grade and since there would not be much machining involved it would not be to hard.
I think that once the machining was done on the BP all it would take would be a chop saw and a couple carbide drills. Lee