Ice forms basically at the stagnation points in the airflow. For the fuselage, that would be the nose, a part of the windshield and cockpit roof. The length of the fuselage will not ice up. The wing typically will have arond 6 x 6cm lengthwise and a few cm's cordwise into the airflow (IIRC the Fokker 50 was certified to 6cm ice build up. Correct me if I'm wrong). My rusty calculator says that's about 80 kg in total for a F50 type of aircraft.