I found it strange that the PCB for the buttons in a vectrex controller had three pre-drilled holes for screw connections, when the controller shell had only one. So I did what every maker would have done, I fixed it by making a drop in extra screw post for the remaining two screw holes in the controller PCB.

The controller shell is made from ABS. So if you print these in ABS you can "weld" them in place with a drop of acetone (pure acetone, not nail polish remover). But these fit pretty snug between the walls of the button cavities, so there may actually not be any need for welding or gluing them in place. Do what you feel is right for your controller. I welded them in place with acetone in my own controller.