Why not ditch the copper and just use graphine alone?
It doesn’t bond well to silicon, IIRC.................
Red Badger explained above that it is the two conductors (copper and graphene) in parallel that reduce the resistance and hence provide the benefit of more speed. I still don’t get how you can use a conductive sheathing and not damage the silicone and yet be isolated from the silicone. I do know that the “magic property” of the material gortex is that it allows perspiration droplets to escape, but does not allow water-sized droplets to penetrate. So, you stay warm AND dry. Perhaps graphene works somewhat like that.