lutcus: doing a retopology symmetrically on an unpose head is ok, or eventually on the top of a topology which is topologically symmetrical can be done with some software, but in such scenario, I would be glad to hear your technique 
lutcus: doing a retopology symmetrically on an unpose head is ok, or eventually on the top of a topology which is topologically symmetrical can be done with some software, but in such scenario, I would be glad to hear your technique