Failsafe should be set immediately after you finish building your miniquad. Failsafe will determine what stick position will be used when your receiver stops receiving information from the transmitter, or when the connection is lost. Setting up frsky failsafe is very straight forward and should take less than a second.
My friend ReadyEdi from Multirotor4fly came up with an awesome (!!!) upgrade for the already great Puffin 210. The upgrade allows to mount the battery in the frame, between the motors – at the center of gravity, instead of on top of the frame.