this is taken from futaba's website
Radio System FAQ
I am using a mix for Dual Elevator, but cannot figure out how to trim out my left elevator. If I use the trim button, it will of course trim my right elevator, but I get nothing from the left one. Is there some way around this?
Unfortunately, no, there is no way to set this up. While based in looks and style on the 9C it does not have all of capabilities of the 9C. To be able to trim your second elevator servo, we would suggest first that you of course do this by hand at the control surface, but if you still need to do a little more trimming you may of course go into your Subtrim menu to make further adjustments. But if you are wanting to trim in flight, you will need to purchase a Synchronizer.