Optic Mounting Options

[HerkyBird]

The esteemed Mr. Shufflin built a Mini-G for me several years ago. At the time, I opted to go old-school...no ultimak rail, just irons. The old peepers are starting to struggle with hitting anything out past 200 yards, so I'm looking for opinions from folks that have optics on their Mini-Gs. What do you have? Pros/cons? My options, as I see them...

1. Ultimak with a LER scope. Is it even possible to go back and add the Ultimak at this point?
2. CASM mount. Understood that I need a Holbrook device. Is it possible to load the rifle with a full en bloc after manually ejecting an empty clip?
3. M1D mount. Would I need a new barrel for that?
4. M1C mount. Any opinion on which is a better or more viable option (D vs C)?

I'm sure I am missing other options. In a perfect world, I'd like to be able to put a standard eye relief scope, either offset or center-mounted, and still be able to use the en blocs. Not against the Ultimak at all, but I'm afraid I missed the boat. I should've had it done when the rifle was built. Or maybe gone with a mag-fed.

Thanks in advance.