The fact that it is in Dorian mode is why I really dont feel you can use the !Vminor chord..it doesnt feel right(ie Gminor for the starting note, or Dminor if you are using Aminor shapes for the song).Trouble is, G major doesnt do the tune any favours either. I think this is a very difficult tune to harmonise satisfactorily(if by harmonise you mean using chords with three notes in them).