ORIGINAL: Dauntae
Get 2 y harnesses and in the radio go to wing type and put flaperon (flaperon wont work unless you set it in the programming but this allows you to use two channels for ailerons) put both right servos in one harness and both left in the other, Channel 2 and 6 are what you will plug the Y harnesses into this way you can adjust both ailerons on one side together with subtrim if needed.
Dauntae
Dauntae hit the nail right on the head. It's a built in dedicated flaperon function in the XP8103. Gives the most control using up the least resources on the Tx unlike using 2 channels to get a single channel result.