[plonker]

Following up on this.
I've discovered that both the "Cad technik" & "b-square" scope mounts do NOT have the correct screw thread for the ejector screw.
The supplied hex bolts are very close, but not dead on. This may be what's causing the thread damage as the one I got with a used Cad-Technik had damaged threads. They will screw in with oil & force, but not properly. That's probably why LocTite is recommended.

Fortunately the screws seem to be a softer metal than the reciever sidewall, so the damage is confined to the screw itself.
I'm currently awaiting a #3 BA bolt that I ordered to complete my mounting.

 

[plonker]

I think you're right.
I'm planning on using a 4mm to replace the cross pin on the rear sight.
The diameters are so close that all I have do do is polish of 0.005" for a snug fit in the existing holes.
The difference here is that I'll be using a metric nut & loc tite instead of burgering up the threads as a locking device!