How do I stop the tool from machining past the boundary on a negative shape (dish)?

In Step 2, Material Size and Margins, setting the Symmetrical input value to 0.0 allows machining past the boundary enough to completely machine the model and this includes the sides of the model.

However, if you set the Symmetrical input value to a very small amount, 0.001" or 0.02 mm for example, the toolpath should be restricted from going beyond the edge of the model.

As this depends on exactly how the model was created and saved in a 3D modeling program, it may not work in all cases.