Thanks Simon, that is most helpful.
I have been trying to work with model mixes for visualization and I fee like it isn't working like it should. Perhaps someone here has some more experience. I can only seem to assign a layer to a model mix. And then when I assign that layer it only plays the movie file. I can't control any other aspects of it. If I assign another mix it only seems to make it white.
I tried with built in models and custom models and I get the same result.
Can anyone point me in the right direction?

Thanks!