Forget the whole picture of turning this into a usable rifle for the moment, just focusing on this one point for an idea...
Say you had a flat bar of metal with two holes for the action, you sit the action down on top and screw it in so it's only held at those two contact points - There is no surrounding stock, no rear of the inletting to absorb some impact, it's just the 2 screws and the base.
Could a rifle work well mounted like that or does it need the inletting supporting it really?