The gas tube and receiver covers are about the 2 least stable places to mount optics. I can see it for a flashlight maybe. If you want a stable optics mount on the SKS, you really should consider the Millett mount that uses the rear sight base, a side rail mount, or one of the gunsmithing mounts that screw into the receiver. ATI and Choate makes them. The ATI model makes you remove the entire mount to remove the bolt carrier and bolt. The Choate model does not, so it's my favorite of them all. I have a red dot sight mounted on the Millet model and it's fairly stable. There's a far better rear sight mount that the Millett, but the name eludes me at the moment.
