Christie recently released a new Duel-Projector system that addresses many of the issues with double stacking. In this video I talk to Brad McGill of Hoyts Cinema Technology Group who has done one of the first installations of this new technology.
See Christie video on Duo here (http://vimeo.com/46386575)
Christie Announcement (http://www.christiedigital.com/en-us/news-room/press-releases/pages/the-future-of-premium-theater-experiences-to-be-powered-by-new-christie-duo-solution.aspx)