I use the same setup as T.O.M on my 35% Extra. The A123's are the only way to go! If you look at Wildhares website he has a package that is plug and play. One 2300 pack should be plenty for your plane. The battery plugs into the smart fly super switch with a deans connector, then you have 2 leads from your switch that go into 2 ports in your receiver. Really, really simple.
As far as a way to kill your motor I just use the throttle kill on my transmitter to kill mine. No extra weight of a choke servo and no opt-ikill to go bad and kill the motor when you don't want it to