Thanks to the brilliant design from David Windestål of Rcexplorer.se, I built a folding tricopter based on the custom FCF3 tricopter Flight Controller. The tricopter consists of three carbon-fibre booms with 2217 size brushless DC motors mounted on each. The rear boom uses David's tail-rotor tilt mechanism to control its thrust direction. The folding booms are held in place by friction between the upper plate (FCF3 PCB) and the lower carbon-fibre plate. This friction is adjustable based on the tightness of four M3 screws.
Powered from a 4S (14.8V) Li-Polymer Battery, the tricopter theoretically should be able to fly for 10-20 minutes, but I have not flown enough to verify this. On a 4S pack, the model has plenty of power, and manoeuvres quite well. The model also has a custom 3d-printed canopy (printed on my Prusa i3 MK2) to protect the reciever and FCF3 header pins.