Using dust cover optics mounts on a Kalashnikov is not the best method. The dust covers are flimsy and will not hold in place very well, and will need to be re-zeroed every time you remove it.
Physics dictates that given the same recoil, a heavier object will shift more than a lighter one (iron sights on a dust cover are fine - they don't weigh very much).
If you want an 'over the centerline' mount, you should look into a Beryl style rail:


Or an Ultimak rail (this is not good for scopes or other short eye relief optics, as it sets your optic forward over the gas tube):
There are also military grade options that mount your optics using the milspec mount found on many Kalashnikovs:
