First off, whats the goal? Plinking, hunting, bench shooting and what length barrel are you going for? That would be my starting point and then work the internals to fit your intention. You may just keep it stock and only use an o-ring mod, or you may end up with a Huma reg with Tim Hill internal parts and make it a consistent beast with really low shot count or a high shot count plinker. Adding a Magnum Air bottle adapter, cf bottle and a ninja reg makes the entire tube a plenum and great for a rifle length barrel. Add a Cothran valve and transfer port on top of that and you have a monster in the making. All depends on the intention. Much easier to help you out with more detail knowing what your goals are.