Toon Shader Outline Width too thick?

I am using the built-in Toon Shader, and on some models the outline thickness is perfect, although its at the absolute minimum of 0.002. On some objects though it is much thicker and looks bad. Is there something I need to do to the model? I organized my smoothing groups how I wanted them. In the picture the two trees have the same material on them, but the smaller tree's outline is much thicker than I want. How can I make it thinner?