www.projectorcentral.com has a calculator for that projecto to show how big of a screen you can use from where the pj is mounted.
The Cardas are a nice pricepoint but if you are spending the coin on 1080p don't shortchange yourself on the screen.... look at the Vultec Silverstar or Stewart Firehawk both are considerably more money but you will be changing pj more often than screens... my Vultec Silverstar was the best investment I could have made (looks likes a plasma in dynamics and perfect off angle viewing with no hotspots..) The Vultec is not the screen to get if you have ambient light because of the silver screen.
www.avsforum.com has tons of threads on comparisons of screens and how they work with each pj... also go with the larger 3" black border so you can shoot over and not have to zoom in and out all the time depending on sources..
Nice PJ your friend is buying!