Quote - By the way, did you find symmetry easy to achieve when making morphs with Blender?

Yes it works really well however if the mesh is not modelled symmetrical ( mirror opposite ) you can have problems. The more asymmetry modelled in the worse it gets but If the mesh is modelled  with subtle asymmetry it actually makes your morphs look more realistic. 

Did you model Antonia with some subtle asymmetry? I haven't noticed any problems using symmetry when sculpting.