One more question while I am thinking about it. I used a similar setup that todd had the other day where I had 3 LED walls. I had...
Mix 3 - across all 3 screens
Mix 4 - screen 1
Mix 5 - screen 2
Mix 6 - screen 3

Mix 4,5,6 are transparent and flat locked to corners.
What I had was a situation where I wanted to put IMAG into one screen, say screen 3, (Mix 6), and leave content running in screen 1 and 2. I needed to fade in the IMAG while the content was running in the background.

The simplest way was to have something running in mix 3 across all 3 screens and then just bring up mix 6 over it.
The problem though is when I would bring up mix 6 to something less than full intensity I would see a blend between the background Mix 3 and Mix 6.
To try and fix this I put a layer of black at full in mix 6 "behind" the IMAG and "on top" of Mix 3. I would still see through mix 6 and see a blend of Mix 3 and Mix 6. My IMAG would get slightly "brighter" when this layer of black was added but it would not act as an opaque layer as I hoped. I even tried making it a mask and that didn't seem to work either.
It would only work if put a scaled layer of black on Mix 3 on top of the video content and "behind" mix 6.
Is there a better way of doing this or am I setting this up wrong for this situation.
Thanks