Issues using Orangerx R800X receiver with Multiwii board

[Quadcopter]

I have built a Quadcopter 450mm frame, multiwii v2.5 controller, 20A ESCs, Emax 2213 motors, Orangerx R800X receiver and Orangerx DSM2/DSMX transmitter module in the Turnigy 9XR.
I am having issues with the Orangerx R800X receiver. I can bind the transmitter to the receiver but the receiver doesn't seem to be able to talk to the Multiwii board. I am confident that my wiring is correct.
Has anyone got the Orangerx R800X receiver working with the Multiwii V2.5. I am using the latest Multiwii software V2.3
Any help appreciated

[Quadcopter]

Connection issue resolved. There was a wrong config.h setting. #define SERIAL_SUM_PPM was NOT commented out. My receiver is not PPM SUM Receiver.

Now have stability issues. I cannot get my quadcopter to rise vertically from start. It always wants to go sideways. I have read many posts about this problem in this forum and other forums. I have done all the calibrations and have set YAW midpoint to 1500 as suggested. One thing I have noticed when testing on the bench with propellers removed that the midpoint of YAW jumps around a bit and when I increase throttle YAW goes up to 1506. Is this normal ??

Any help appreciated

[Arakon]

Yaw isn't the issue, ALL values have to be at 1500 when centered.