I did some asbract "closed" polylines in autocad, then imported the acad drawing into rhino, then selected the outer edge pline and extruded it, then selected the inner plines, extruded them as well, then did a boolean subtraction, then did a mesh from nurbs object, then used the "bend" command to add curvature. Whew!!!!!! did you understand all that? (knowing you, you did:-) I can send you the files if you want. Davo