"For the best results only use Ambient Occlusion on the IBL. Better yet, set up the AO in the Materiel Room"

I'm just nitpicking here (your advice was good), but the quote above forms a contradiction.

The material room AO node calculates shadowing due to occlusion. However, there is no way to apply it only to IBL light.

If you plug the AO node into the Diffuse_Value, or plug it into a Diffuse node, you are interfering with the diffuse reflection from ALL lights, not just the diffuse part contributed by your IBL.

So mat room AO is equivalent to enabling AO on every light you have.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)