The Eclipse is a sport TX and as noted previously was not designed for dual elevator servo use. Yes it does describe how to utilize it as such, but with limitations. The trim is one of the limitations as well as the switch utilized to activate same.

Had Hitec aimed the Eclipse at the larger airplane market rest assured it would have a mix designed around dual elevator applications. And yes its a shame the engineers did not see the need for this feature of this otherwise well equipped sport TX.

FWIW: The new Optic radio system has this feature and more.