With respect to these sight mounting bases.....
I've worked up a system for making them, refining it with trial and error, if anyone wants to give it a try.
4"x4"x1/4" 6061 aluminum angle is available from aircraftspruce.ca.
I bought a foot, cut it into four pieces. Clean the edges up, cutting to final dimensions. I used a power hacksaw and a mill, because I had them.
There are three mounting holes on the gun, for 1/4-28 screws.
Drill the very bottom hole, just above the lower edge of the piece. Get it centered. With the aluminum stock I used, it is possible to see the battle sight underneath the sight mounting base.
I made a little 1/4-28 stud the thickness of the base on the gun; cut a screwdriver slot across it. Small hole drilled through, on center. Made a little hardened pin, with pointed end to fit this hole.
Install the little stud with pin in one of the top mounting holes, fasten the bracket to the gun using the bottom hole. Wiggle the bracket into position until the top of the bracket is exactly parallel with the top plate of the gun. Measure carefully, front and back. Hit the bracket, the little pin will mark where the hole should be. Centerpunch and drill. Repeat for the third hole.
Check for fit.
Measure from the side of the sight base to the sight line of the iron sights. Add 1/4". Use this measurement to carefully scribe a line of the top of the bracket. This is where the holes for the scope base will be drilled.
Select an appropriate scope base. Drill and tap the bracket for the mounting holes. Scribe and cut off any unnecessary width from the top of the bracket.
The scope base can be a suitable Weaver, a piece of Picatinny rail, whatever suits.
It must be short enough that the top cover can be swung open, and the backplate slid vertically.
If necessary, use shims under the scope base, or windage adjustable rings to get things aligned, if the internal adjustments of the sight are insufficient.
To finish the aluminum, blast and spray.