I have a futaba14mz with a TM-14 2.4 GHZ module and R6208SB receiver. After I upgraded to Copter 3.4 and did a quick test flight which went well, I decided to tidy up the RC 9 to RC 12 wiring on the pixhawk i noticed noticed something strange on mission planner in the status page i was getting an input on ch13 to ch16 when I switched channel 5. After a bit of investigation I discovered that channel 5 was assigned to virtual channel 1 to 4 on the radio after changing the switch allocations did indeed output to channels 13 to 16. As a further test i connected the AlexMos Gimbal over serial to the pixhawk and was able to work pitch, roll, yaw and command to channels 13 to 16.
Hope someone finds this useful.
David Ardis