I thought about making it one figure with two actors. But I'm not sure how to do that - I've only made props, not figures. However it's done, it's important that the inner sphere is invisible to raytracing, while the outer is visible to raytracing. I presume this requires two separate actors, i.e not a single prop. If anybody can teach me otherwise, that would be cool.

As long as Poser isn't lying to us, :) (ie: As long as there's no technical thingie with materials going on that isn't otherwise obvious) you can set up a group in the normal object panel to be invisible to ray-tracing while other groups are visible to it. It's just a checkbox click. I suppose you could also hardcode it by editing the .cr2, but that wouldn't really be necessary as long as users knew to leave it at its default setting. (Note: You'd just have two groups, one for the outer shell and one for the inner. You could use a null or rig them to rotate independently, I suppose, if you wished. All in the same "figure.")

PS - This is really cool stuff and I'll stand in line for it. :)