Hi Alan, The ones I have seen are the cinema made by harkness and MPI? .
The Percival zone of comfort is the stereoscopic real estate between you nose and the very back of the parallax perspective all the way 20 feet behind the screen. Within that zone is that all the 3-D action occurs. I like to see nothing blocking the action, with these silver screens there is mottling (a word you taught me) and there is a cheese grater effect, like where the perforations are punched they stick out a bit giving it a half hazard consistency, that pretty much gives the effect of installing a Badminton net in the middle of a space, you can see who is in the other side, but the zone is split by this net. I say the perforations on silver screens coupled with the mottling totally break up the Percival zone of comfort illusion.
A woven white screen would not cause this, but it will not work with RealD so I am very interested to see what you find out.