Are you sure of that ? I have seen side attached mounts in british Mauser and those rings goes over the action, very similar way as in these fotos below.
With Mannlicher action you just can´t attach the rear mount same way as Mauser so only reasonable way is just screw it to action sidewall. RECKNAGEL sell upper billet rear mounts for MS so just buy pair of them for this project.

By the way; the only reason why I didn´t buy this rifle was just money, or actually, the lack of it.