I built the Senior with rudder only. I put a seperate servo on the front wheel and plugged into the rudder channel. I plugged the rudder into the aileron channel. When I built a wing with ailerons, they plugged into the aileron channel. The rudder went to the rudder channel wih the front wheel. That made for an easy transition to four channel.
Start building! Awesome feeling watching something that used to be a box of sticks take to the air.
Mike