Ok that works, indeed. Have yet to check how much it hurts performance if I use many.
Two links that are explaining the solution in a detailed way are:
Although part at the end of Mitch’s video explanation (starting at min 9:05’) is not needed anymore as the ‘Stereo Layer Type’ parameter in the Stereo Layer component now admits “World Locked” and it appears to have been correctly implemented now.
The problem in VR is that controler 3D models, that from a 3D logic criteria should be in front of the stereo layer, because are nearer to the user, are rendered “behind” (since the stereo layer ir rendered on top of everything). To solve that, the stereo layer is apparently cutting out a part of itself with the silouete of the controller, where the controller is, so you can see it “through” the stereo layer, giving somehow the apparence that the stereo layer is behind the controller. This sophisticated behaviour comes with a handicap: this “cut” itself is a “hard” one with no antialising at all. So while the widget shows itself almost perfect now, the frontier between the controller and the widget, doesn’t. It’s much les noticeable and annoying that the widget aliasing that solves, but still not ideal.