I need them in some cases..
in others I do not

I need them for the regular renders
I do not need them for "mask" renders (where I have to render all white over black) because carrara's alpha channels for tif or photoshop are not tight enough.  I can edit them in aftereffects, but I start losing detail when I do that.

anyhow
based upon all the info I'm getting, its not possible to do what I want currently in carrara.

too bad, that means I have to write something (or maybe someone else will write it)

thanx all
BT