Yeah... some use them some don't... when I built my first cat a good friend suggested adding the rudder... the second servo also helps balance out the plane. The rudder really makes this plane shine as a sport/speed plane... take-off is easier in wind and you don't have to do a Pylon launch unless you want to... it really help's the plane in the air also... makes it more sport like... just for the heck of it I built one without rudder... I added it after the first few flight's once you go rudder you'll never go back

John