You can fly the plane without rudder. But the rudder is the most important when choosing servos torque wise, and for reliability. Think about this, the rudder is directly in line with the prop blast, even more so than the elevator. The elevator and ailerons are take a lot less torque than you think. There is somewhere a calculator that tells you how much torque you need, and the rudder was way more than the others. I think that on a 28% extra with 3d surfaces, the aileron and elevator only needed 45oz in, and the rudder needed 168oz in!

just my 2 cents.