I baught my material from
Dazian. Great material and its sold off the roll in any length so the limiting factor is the width. Their Matte Non-Perforated comes in 54" & 86" width, so the max diag without a seam is approx 175". They also have a Matte Perforated material if you want your speakers behind the screen, as well as grey and bone material. They say they can make the material 80 feet wide without a seam. And they will cut any length an send it to you.
cheers