I have a converter which takes in mm5 model data and outputs CF-compliant netcdf. The netcdf files load fine into the IDV. The
following url should get you an example file (about 40meg)
Also, we provide a zip of the converter, including the Java sources:
I recall that in producing the CF compliant nc, the nc file does not actually need any lat or lon variables in it at all, just
the correctly named Cartesian x and y and the projection variable.
I hope this may help, feel free to ask questions