geez, I hate to make my 3rd post as disputing someone, but my experience tells me I must.
Receiver cover scope mounts on SKS's simply don't work well. They may be fine, at first, but after you've shot some rounds with it installed, it will invariably loosen up and repeatability will be a thing of the past. Whether the base is welded on the cover or screwed to cover, the covers fit to receiver is what will loosen up.
Even the Millet mount, that attaches in place of rear sight, has a lot of issues with side to side movement. I hear there is another mount that attaches there that may be a little better but I have no experience with them.
The only ones that truly hold zero is the type that require drilling and tapping the side of the receiver. I hear lots of good things about the Leapers. A shell deflector is generally required with these type, though.