The majority of Futaba computer transmitters can be set to Mode 3 in the menus, then you swap the throttle detent and elevator centering spring inside the case. I do not think JR supports these changes through the menus but I might be wrong.

I use Mode 3. I have a Futaba 6XAS, actually I have two. One is mode 2 and it is the master. The one I hold is mode 3 and it is the slave. It works perfectly on the trainer cord. My reason for using mode 3 is a physical handicap which may very well keep me from ever being a solo pilot. So, I knew from the start that I had to have two transmitters to accomplish having a master/slave setup that will work for me and for any ‘regular’ US instructor.

If you plug servos into ‘odd’ channels to create your own version of mode 3, you’ll never be able to hook up on a trainer cord and you’ll have all of the ‘mixing’ issues previously mentioned.