Project edges of a surface onto a plane normal to surface

Hello,

I have a set of 3D surfaces that I need to project onto a plane to create an extrusion; however, since the plane is at an angle to the surfaces, and the surfaces have edges using Style, they cannot be projected using the Project tool. Below is a preview of the surface viewed normal to the plane, and there is also an image where the edge is visible zoomed in.

I am making a mold, or "negative" of this part, so the only task that I need to do is project these edges and extrude to each individual surface within the part. Basically, I will take the outside profile of this plane and extrude up to the surface, like the photo with the red arrows shows. I have explored unwrapping the surface using Flatten Quilt, but that did not help. I also tried a few boolean Remove operations but they also did not work to create the mold. Is there any way to project these edges onto the plane to create an extrusion? I'm using Creo Parametric 10. Let me know of any questions, and any help is appreciated.