I did a test piece in the spline modeler of a typical section of locomotive frame, importing a compound object saved as Illustrator 8. The front and back faces with bolt holes are perfect, fidelity jacked up to 500. However, I need bolt holes thru the top and bottom faces as well. I duplicated the shader  and threw a texture map into the alpha channel - map had 3 holes (black with white background) which should have showed up where the red arrows indicate - and applied shader to the top face domain. The middle hole came in great, perfectly round so I know the map is oriented and projected correctly, but the 2nd and 3rd holes on either side don't show (or are very, very faint). The top hole has no sides of course, as it doesn't physically exist, but it looks good and I could live with it, if only the other "holes" would show. And I can't see any way to change shading domains short of converting to vertex.

Mike