Circular Surface for Kangaroo

To the beautiful mass brain...

I am wanting to use a circular surface with kangaroo. 

Is there a way of producing a circular surface in which all the control points are located (a) within the surface and (b) the external points lie on the boundary? 

I understand the NURBS concept and that of control points and the resultant surface being a mathematical representation of their various influences, but is there a way to produce a surface which doesn't follow these rules or is this no longer Rhino?

I did get briefly excited when i rebuilt the curve with a degree of 1, the control points all appeared on the boundary, however when i made this into a surface, the points were once again on the outside of the boundary. 

Many thanks

J-P