Paul,
Actually it's not so durable for stage gigging, but is also necessary for sitting play because many of long scale basses have their lowest position too far to me.
They are kind of primitive things made with certain nuts, a screw and shrink tube. I had to a bit widen inside of strap button.
You should find enough long screw you desired, and get nuts in which the screw can pass through. I piled some nuts for the length and glued, then wrapped up.
Shinichiro
