First - one question according highlighted area on the picture. It is part of opening part of the rear canopy. The question is, what remains there when the canopy is open? Is there same/similar fixed part? Or just kind of small semicircular metal plates to which is open part locked when closed. (I hope you understand what I mean...)
Congrats on your work! simply...?
Regarding your question, I have no pic whatsoever, but if Ruskies kept with their tradition, it should look just like on your drawing (red outline), but recessed for the depth of transparent part. Usually, there is a lot of wear around the holes, and they should be rounded in profile (cross-section) as well, like a throat or funnel. This way it's easier to match the fastener with the hole
If you cannot find appropriate picture, any walkaround of Soviet aircraft will do. Some servicing panels on Mig-15 are designed in the same manner as on Mig-21, so I believe things like that are hard to change (if it works - don't change it).