Thanks Peggy - in that case, Mark Caldwell came up with a good Godrays trick - punch holes in your clouds with transparent cylinders - Godrays seem to work best with heavy clouds and smaller well-defined holes. Use volumetric lighting, spectral atmosphere (available in your version I guess), a wide angle lens and with the camera rather distant.

If you get "grainy" clouds (lack of enough samples), turn up that "Quality Boost" slider in the Spectral Atmosphere "Sky, Fog and Haze" tab to about 2. Mess with the sun angle Vs the cloud holes, size of holes, angle of cylinders. Of course the darker your scene, the more your Godrays will stand out.