Hello, I managed to do it finally but it doesn't work 100% as I would like to....
I used the AUX1 as normal configuration linked to flight mode 1 to turn on/off and works pretty good.
However, I am using the GEAR channel for the dual elevators. I slave ELEVATOR - GEAR..... 100% and they move together. However, in the up direction both servos have the same travel. but in the down direction the elevator (the one plugged to the gear channel) has less travel than the elevator plugges into the elevator channel. I tried increasing/decreasing the travel of GEAR but not improvement......
I prefer to avoid the Y inversing harness as I used it already and it failed by stopping one of the servos! I was lucky to manage to land it safely.... so, no risk it again....
My ATV for elevator and gear are 100% in both directions.
any ideas of why????

thanks...