I should preface this by stating I have personally not done this before. I suspect there are many here who have and can provide more details than myself. A while back we had a project that required an arched moulding. We used several templates of the arch attached to our board stock to cut the profile.
I think you need to start by not looking at this as a traditional crown moulding with a spring angle and such but as a flat arched moulding you can apply to the face or top of your furniture. In other words your board stock will need to be thick enough to provide the look of springing forward off the face of the cabinet. I would suggest you make a template of the shape you want the top moulding to be. Then lay up and cut out your board stock so it is the same shape as the template. Next I would make a template of the negative top arch or shape and attach the top of your now shaped board stock to it so the face of the stock and template are flush. This gives the router a surface to ride on and a surface to attach multiple other guide templates to. I would then begin working the face of the stock with my router, multiple negative templates for the router to use as a guide, and multiple bits to shape it similar to a crown moulding.
There may be a much better way to do this. I am sure there are machines that could make such a moulding. If I could turn my crown profile sharper bit on an angle and not have the base or table obstruct the cutting of the profile there would be a way to use it. I cant see any way to do this with the tools I have.
I am interested in what others have done.