Wrong forum, sheesh. Seriously though, I'm using one now, they're slightly more than 4 x8, 49" x 97" to be exact. Cost me 13 bucks I think at Home depot. Works just fine-- shockingly fine actually. Some people go," oh, you went and got ya one of those plasma dealie things, eh? Looks grand!"
For snobby me, though, it's temporary. I want something bigger than that, and in 2.35, (and with more gain, that is, a Hi power. Do-able is a neutral gain (?), I guess, but what do you want for 13 clams.)
For others though, note it's a permanent solution. There's AVS forum devoted to DIY screens. (LOTS) of info on Do-able, or just painting walls or . . .