Scale relation between real and virtual world, with steamvr (HTC vive)

Hi team,
I'm working with the steamvr (HTC vive), and I'm trying to change scale relation between real world and virtual world. Like if "worldscaleFactor == 2", one step in the real world would be two steps in the virtual world.
Also ideally the new scale factor would only apply on the x and z axes.

Probably not the best practice in a game, but it's for an experimental project.

Please let me if you have any clue.