I would have to look closer at mine to see if it had 4 free mixes. It would take four to do this.
mix 1: ELEV to FLAP using switch in down position
mix 2: ELEV to AILE using switch in down position
mix 3: ELEV to FLAP using switch in up position
mix 4: ELEV to AILE using switch in up position.
You would have to set your % to + for one pair and - for the other depending on how your set up was. I use one of my mixes for the ELEV servos so I don't have enough mixes to try it but I can't see why it would not work. Before you mess with it do this. Copy your model over to another model # and change the name a little. Like if you model is EXTRA300. After you copy change the copies name to TEST300. This way you can tinker all you want without messing up your original model program.

David