Plane texture casting shadow

Hi guys

New user of Vray for Rhino here. I don’t know if I’m just not getting something, but I simply cannot get a plane with a simple bitmap (a background) to disappear and not cast a shadow. I need a reflective steel object, but with no shadows or visibility of the bitmap plane.

I have ‘only in secondary’ on and ‘cast shadows’ off. Seems to have zero effect.