Hi Emma,
I tried this but unfortunately the Apacer media player wouldn't play out the file onto the mapped object the same size as the laptop output - despite saving the file in Syphon Recorder at the same resolution as the projector output.We also tried it with a WD Media player but with the same results.
Perhaps if you try different media player or fiddle around with the screen resolution settings you'll have better luck than us...?
Good Luck! & please keep us posted on any developments.
Tom