I don't know for sure if the method will transfer over to my usual skin shader, but I have reasonable expectations. If I had to guess why it worked, I would say it has something to do with how Carrara calculates the light. Before I changed the figure's size, her head was only a few inches in diameter. You could imagine the light waves (or particles, depending on how you look at it), whose size you cannot manipulate, as being much too big for her to look realistic. It wasn't until I brought Vic up to human proportions that she was in scale with the light in the scene. Does that make sense?