I am having trouble unfolding cones in sheet metal format.

The part is designed with a thin revolve and it has a straight line or face on the side that has the extruded square hole.  Everything I read says that this should work if I pick a line or a face on that side when I insert bends.  I have tried a triangular cut for the seam with the vertex of the triangle on the origin, and I have tried to cut half the cone, and unfold just half.

I know that someone out there knows how this works.  I have not had great success with my technical assistance team on this one.  Help.

Please see the simple attachment.

Jack