With dark walls you are combatting reflected light coming off the screen mostly along with light coming through the windows. The screen wall is actually not that important in a dark room, but becomes more important with ambient light. Still, most important is the floor, ceiling, and walls about 10-15 feet in front of the screen.
Darker and flatter paints are the key to making it work best. But, ambient light control, especially light control near the screen is what will make the image look best. A set of good curtains on all the windows is great, but you may have great results if you just close the curtain which is closest to the screen and be very happy with the image. Not as good as when all the curtains are closed, but more more welcoming of a space.
I'm not sure why you are looking at the silverstar screen. As already said, several times, you don't want a huge gain factor on the screen, but a smooth image.
For your reading:
http://www.projectorcentral.com/vutec_screens.htm
106" diagonal is appropriate size for about a 10-13' viewing distance.