In the 10C, you'll need to use a pmix to have dual elevators. Just select any Pmix and turn it on. Make elevator the master channel and an unused channel the slave. Turn trim ON. Set the mix amounts and you're "good to go".

To convert the 12FG from Mode II to Mode I, you need to move the spring and ratchet between the sticks, reset the software, and then recalibrate the sticks. This requires the service program, which is external to the transmitter, and available only to authorized Futaba service centers.