I'm using a DX18 to fly a plane with an APM 2.5 but I can't get the elevons to mix properly. I set them up on the radio and not matter what I do they don't move in the proper direction in FBWA mode. I tried switching the channels where the servos plug in but no matter what I do if I get the radio programmed ok FBWA isn't correct and if I get FBWA working I can't get the radio programmed to work in manual. Did radio calibration several times and tried all of the reverses on the GCS too. Any suggestions?