can you draw me something of what you are actually trying to achieve?
- im trying to help other people as well.
this is something that quite a few people have asked for.
but there are sufficient variations - that not every solution works for everyone.
Ideally the mask layer could be any one from 2 to 7 and every layer above that would appear in the mask.
That way you could have layers 1 thru 4 as background layers appearing as full screen. Layer 5 as the mask for the alpha channel and then still have 3 layers to muck around with inside the mask.