Overlay requirements for 1:1 masks used in x-ray lithography require robust mask mounting techniques which are relatively insensitive to uncontrollable imperfections. Small variations in mask flatness or mounting surface flatness should not make the mask unusable. The cases of 3-2-1 pinch-type kinematic mounts, stiff vacuum pad mounts, and full surface mounts are investigated here. The results show the kinematic mount to be superior in its insensitivity to the original equilibrium configuration of the mass after bonding.