Fuselage and Fin Covers are designed to keep the worst of the elements off your airframe. They involve a great deal of work as they generally have most of the aerials fitted to these areas. Because of this they take a lot more time to make and care needs to be taken when fitting them to the aircraft.
When necessary the fin portions are fitted with hook and loop and sometimes the top sections come with a “top hat” design as this is the only way the aerials can be accommodated