Designed to tow the giant Messerschmitt Me 321 glider, the Heinkel He 111 Z has achieved relative success in this role. The link below provides an entensive report and photos showing a bit of its history:
http://aviacaoemfloripa.blogspot.com.br/2011/02/um-rebocador-para-o-gigante.html
Hope you enjoy and I count on your visit!