aaargh! don't render these things as AVI's!

Never ever, not even with zero compression.

Compression makes compositing a bear, because you'll never get a clean edge or alpha, and recompressing the composite will produce lots of artifacts.

When rendering Poser animations, save as numbered TIFs . . . Poser will save out a perfect alpha with each one.

Will make your life way easier.

On the PC, I use Discreet Combustion (an old version, which works just fine). Jahshaka seems very similar.

(BTW: love your "Corman's Comeback" image)