With any flybarless system and the ReactorX(2) you will want to setup as follows:
Receiver -> Flybarless controller -> ReactorX -> Servos
From the servo outputs of the FBL system, connect the ReactorX via the RX ports and leads. Then the servos are last, and connected to the SX ports of the Reactor.
All you want from the FBL system is the servo signals. The ReactorX is last in the chain before the serovs so your servo does not have losses from all the connections up to that point. The servo gets all the current and voltage it needs direct from the ReactorX. Everything else up to that point is just the servo signal getting passed on.
Power to the FBL controller, and reciever is passed down from the 5.2V side of the Reactor regulator via three leads.
I'll be posting Flybarless hookup info on my website in the near future. If you have any other questions feel free to contact me anytime.
Throttle, gyro etc, all get hooked up to the receiver like usual. The RX will be at 5.2V regulated.