Has anyone used the scout mount that attaches to the rear sight block. How much of a sin would it be to have a scope rail mounted to the side of receiver

Traditionally, milled AKs didn't have side rails, and I'm not sure how difficult it would be to attach one to a milled receiver.

Also, which mount are you talking about? There are quite a few mounts that attach to the rear sight base, from scout mounts to full railed dust covers.

I have an attero arms mount.  It replaces the rear sight, allows to mount a red dot, and also gives you a sight on the mount.  It is solid and I love mine.

Thanks for the reply, I posted this question in the wrong forum should have posted in optic section.
The mount  I`m thinking about using is very similar to Attero mount , it looks like best way to mount
dot on rifle without drilling the receiver

this is the scenario UltiMAK has perfected.

This...And it will co-witness. Almost anything else will have you doing the "bobblehead" thing behind the optic trying to find the dot due to the optic being too high. If you want to check it out on the cheap grab an Ultimak and a Bushnell TRS-25 or Primary Arms RDS and see if you like it before dropping serious coin on an Aimpoint T or H series. Just Got back from the range today with a TRS-25 on a UTG quadrail and when the budget allows I'll probably upgrade to an Aimpoint T-2.

Once you drill that milled receiver for a side rail most will consider it ruined.    

Yup, don't do it.