Why not? Often Convertibles are allowed to tow a heavier trailer than the Wagon- or Sedan-version of the same model, as they have a stronger body structure.
I've heard that from acquaintances, who bought a Golf Cabriolet for that purpose.
From others I've heard, that the Fiat Ritmo Cabriolet was allowed to two 1450kg - very much for a car of this size. And it was too much indeed, as they have recognized with a large horse trailer.