Dunno mate, I've only seen the pictures on their site. My screen (on it's way courtesy of ScreensUK and TNT) is an ellie, which has removable/adjustable brackets to aid mounting.
If your joist is parallel to the screen, you'll have to watch that you get both screws to bite properly into it. If the screen is at right angles, you'll obviously need to hit two separate joists with the screws or use noggins.
A noggin (for those who don't know) is just a cut down piece of joist, the same length as the gap between joists, that you attach between the joists, usually with long nails going through the joist into the end of the noggin.
Best to use a powered frame nailer rather than a hammer. This is partly because it does it in one operation, quick and easy with less plaster dust being shaken off everything, and partly because nailguns are such fun to use ;o)
Enjoy
Martyn