I discovered a problem with my idea, associated with my powers of observation. - What I did not notice is that the hole I was looking at is of an oval shape, not round. It is this way so that the trigger pull adjustment screw can travel into the hole at an angle that increases as the trigger swings on its pivot.
It looks round on a casual inspection, but when I took a closer look I discovered that it is oval, and why.
A second method occurred to me, but it will require taking the gun completely apart as a hole must be drilled and tapped in the trigger housing, from the curved rear surface.
(You need to Login or Register to view media files and links) A hole drilled and tapped from the rear of the housing where indicated would (with a set screw) provide a variable stop that could only be adjusted with the stock removed.
As the trigger pivots, it eventually contacts the rear of the trigger housing. A set screw poking out where the contact occurs would be able to eliminate almost all of the over-travel.
Now I'll have to decide it it's worth the effort, to me. - And I'll keep trying to work out something more suitable, that hasn't occurred to me yet. - I have my good days and my bad days, you never know...