Using the above guide and with minor tweaking, I was able to control flight modes on the Sport Cub S, APM quadrotors, and betaflight. I used the gear channel for Flight mode and armed with Flap switch. Can you substitute flap for gear on everything in the config? Reversing ELEV or RUDD would NOT give the same result. That would reverse your Pitch or Yaw. I migrated to a DX8, sold my DX6i, and can't test it or look at the available options.
Cheers!
LitterBug