I have a 5' x 7' screen from Screenworks. I do the same thing, project from the rear with a Benq short throw projector. I'm doing away with projection in 2015 and am selling both the screen and projector. It's part of my downsizing with "more is less" philosophy.
My 7 ft DaLite was just over $200 delivered. The frame snaps together, then the screen snaps onto the frame. To hang it just over my head at my console, I attached ADJ 1.5" O-clamps to the fly points on top of my EV SXA-360's, then put them onto 9 ft Ultimate lighting tripods. I run an aluminum pole through the O-clamps and suspend the screen using "candy cane" hooks. The projector sits atop a standard speaker tripod behind me with a wide throw lens. Using 9 ft stands plus the speaker height allows me to elevate the screen above my head (I'm 6' 1"). This setup doesn't add much to your standard DJ space footprint.