I love the lightsabre mockup. I initially thought you were avoiding showing Luke's face altogether — which could work very well, dramatically speaking, and would mean we'd be able to shoot the scene with a stand-in rather than reusing footage.

Re timdiggerm's concern: I think it's another case of where the limitations of what we do can lead to a good dramatic outcome — Luke doesn't want to believe that Vader is his father, so he's been putting off asking until it's almost too late.