While the 9C allows you to use ch 5 instead of ch 6 for the flap servo, not all of the built-in functions recognize this. I consider this a bug, but when Futaba was contacted they seemed to think it a feature (ie, that you could use ch 5 at all). I don't remember exactly, but your problem sound familiar. They told me to use one of the Pmixes to make up for the lack of airbrake feature passed through.

Another thing to consider would be modifying the 5-ch Hitec. I have several old hitecs (555 or 535, I can't remember. Its the older of the two). The chip is actually a 6-channel chip, with only 5 channels brought out to the real world. Follow the signal lead fromt he plug block to the chip. Probably will find the next-door leg on the chip is unterminated. Cut the ch-5 leg loose, and jumper the ch 6 leg in, and you now have a 5-channel RX with 1,2,3,4,6. I needed to do this for my JR radio, which did not have this "feature".

Note my older 5ch Hitec does not work with the Futaba 9C. Apparently the bitstream is too long and synch gets lost. Hitec says buy a newer RX. Futaba says get a Futaba. I use them with my JR, and my 9C runs my Pico Stick. What a waste!

Chuck