Hi Mark, in the future want to make a kind of more full featured "hidden-line" curve generator that would also incorporate projection to a plane.

I'm a little bit hesitant to add in a built in project to cplane option into the silhouette command because 1) it would generate weird results when making silhouettes in the 3D view, and 2) it would tend to make stacked up duplicated geometry when doing solids in other views.

Probably instead of adding in a direct option for this in silhouette, I am going to be adding in a button to the Project tool to make it easier to project curves down to the cplane there. So once that is in place it should be easier to get the result that you want just by using the project tool after generating silhouettes. You can do that now already, you just need to draw in a plane object for the projection target. The tune-up to the Project command will be a "Use CPlane" button that you'll be able to click rather than needing to draw in a plane.

- Michael