[Chimera-users] fitting antibody and envelope protein structures to EM map of virus: C3 and icosahedral symmetries

I have an EM map for a virus that includes an antibody bound to the envelope proteins. The envelope proteins are trimers of dimers with C3 symmetry that form spikes on the surface of the virus. I fit an atomic model for the spikes to the map using icosahedral symmetry, following the very helpful symmetric fitting video tutorial<http://www.cgl.ucsf.edu/chimera/videodoc/SymFitDNAb/>. Now I am trying to fit a model for the antibody into the spike regions of the map. I need to impose C3 symmetry for the antibody for the fit into each spike, in addition to imposing icosahedral symmetry to include all the spikes. How can I impose both of these in the fit? Thanks, ?Mike Kent