You can find others output in flexiIO port (receiver port)https://librepilot.atlassian.net/wiki/display/LPDOC/CC+Hardware+Configuration#CCHardwareConfiguration-ReceiverPortThis means you should use the flexiPort for PPM input if you need it, and set the receiver port as Output.You cannot use PWM input (all wires) and additional output in receiver port.
You do no need extra wires between the receiver and board... with octo, hexa or quad the stick functions are the same. Throttle/Pitch/Roll/Yaw and flightmode.The FlexiIO port (receiver port) provides the extra motor output needed for octo, in fact you cannot still use the PWM input, all wires connected to the receiver.Using a GR18 the only option is use the Next branch (developer branch) that support Hott SumDhttps://forum.librepilot.org/index.php?topic=1910.0