hey, my falcata and another outcast in one managed to almost take out a battleship... granted, it was a bit distracted by other ships at the time, but it also had cruisers and gb's helping it out.
You just need to have an inferno cannon or shield busters equipped in addition to your supernova. The low-energy shield busters keep the cap shields down, and you can land all your supernova shots on the hull directly.