There must be a better way than what I'm doing right now. I have Cineform encoded green screen clips that I first rough cut in Premiere. I then export the timeline as a CineForm High HD optimized .avi and import into AE so I can cut the key. I then bring the matted footage back into Premiere so I can add my backgrounds and graphics. (I don't do that in AE because I haven't figured out how to make enough of the clip play real time with audio so I can time my graphics). I render in AE as Video For Windows RGB+alpha straight (unmatted). I've tried rendering as CineForm AVI RGB+alpha, both premultipled and straight, but Premiere doesn't seem to recognize the alpha channel on the Cineform AE renders. Any suggestions on how to streamline this gratefully accepted.

Alpha channels only supported with Prospect 2K/4K and NEO 4K. The workflow questions I less sure about. Won't Dynamic link help you somewhat?

Thanks for the response, David. I guess I need to consider upgrading.
Does raise a question, though. Why does the menu offer the option of rendering with an alpha if the software doesn't support it?

It shouldn't, we will need to check out that (it is support to be ghosted on the HD products.)