With screens it's a case of suck it and see. I used to have an MRA vario and was never quite sure if it worked or not, I had the blade thing up and down and at all angles, I even put it on upside down once but it never really did anything for me. But, for some people it works a treat.
By the way, if anyone has a standard Gen 1 screen for sale cheapish, I would be interested. PM me.