I didn't explain that too well - I wasn't trying to suggest a conversation was going on between them, just that they are aware of each other, and making that the point of the scene, rather than Han's bad jokes. It's the first moment in the film where the conflict between father and son is brought in, and that should be the sole focus of the scene, IMO.
What I really wanted to do with that scene: when Piett asks Vader what he should do, is take out Vader's 'I will deal with them myself' dialogue and just have him thinking. It worked great when I tried it, added to the drama of the scene - except that the score I replaced the dialogue with is tinny and sounds nothing like it does in the film.
I checked the sound when the carbonite hits the floor, my edit and the original are both the same. I can't see anything wrong with it.