I think a clamping system would work. A ball stud (or something) that mates with a special clamp after it’s inserted.
Something like this for the stud, although I’m aware there’s very little clearance. The ball end would have to be smaller than opening, around 4.1mm.
A specially designed clamp could slip over the top and bottom and tension against the stud
There’s a few obvious problems, but I think they would be easy enough to overcome. Like, what secures the clamp in place, how much tension is required, etc.