Is it possible to remove enough metal to mount a Deltapoint Pro directly?

I would think the MOS plate cut would remove to much material to get the sight to fit tightly.

That's my expectation but I'm no quitter.

The Glock MOS design is absolute trash, better off just getting a non-MOS and getting it milled. My feeling is that *IF* you can get the slide tapped for the holes on that particular sight, then plane the factory plate so it's thinner and drill out the threads (if you even need to), you're good to go.  All depends on whether there's any interference within the side where the mounting holes will go with that particular sight though.

The problem is the only Glocks I want but don't own is a G40. The slide isn't available unfucked.

I stick by my first assessment then.  If you can tap the slide deep enough where the holes through the sight are, you could remove material from the bottom of the MOS plate to make it thinner, remove material from the lip as necessary to get it to sit properly (or just remove it all together), then use the existing holes in the plate and slide as index points, shorten those screws as necessary.

I don't think you could mount directly due to how they cut it with the extractor there, so you'd have to use the MOS plate in some fashion to keep the plane where the sight is mounted above the extractor.  

Other option would be to remove the rear sight and mount it further back, but then you wouldn't have irons.

"Perfection"

I've got (4) MOS models I absolutely love them.

Let me know when your ownership of them fixes the poor mounting design choice so I can also buy a G40, until then, hard pass.