Thanks Mike and Taff ; your posts are encouraging.
BTW: this from the US Patent Office: "(m) Shading. The use of shading in views is encouraged if it aids in understanding the invention and if it does not reduce legibility. Shading is used to indicate the surface or shape of spherical, cylindrical, and conical elements of an object. Flat parts may also be lightly shaded. Such shading is preferred in the case of parts shown in perspective, but not for cross sections. See paragraph (h)(3) of this section. Spaced lines for shading are preferred. These lines must be thin, as few in number as practicable, and they must contrast with the rest of the drawings. As a substitute for shading, heavy lines on the shade side of objects can be used except where they superimpose on each other or obscure reference characters. Light should come from the upper left corner at an angle of 45°. Surface delineations should preferably be shown by proper shading. Solid black shading areas are not permitted, except when used to represent bar graphs or color." http://www.uspto.gov/web/offices/pac/mpep/documents/appxr_1_84.htm.
Also from the U.S. Department of Commerce's "Guide for the Preparation of Patent Drawings": "Drawings may be freehand work, per se, provided they meet the same standards......." and "The Office will accept computer-generated drawings provided....."
So, I think use of SU here (maybe with some CAD for shading) is worth pursuing.
Robin