Before you go through all the trouble and headache the model was intended to be used with a seperate aileron and elevator. like a conventional airplane. That's why they had the Y harnesses installed. But yes it is possible to set it up so it'll fly more like the real deal. I'm going to be doing the same thing to my F/A-18 Thrust vector pretty soon.

In the instruction manual it'll be a little clearer than me. I'm not too familiar with the DX6i, but I'm sure it's about the same as the DX6 and DX7 that I'm using. Set up the tail end for elevon mix. I'm away from my instruction manual but I believe the left elevon gets plugged into the elevator port on the receiver and the right elevon gets plugged into the aileron port on the receiver.

Program your radio for elevon mix and test out the controls to see if the ports need to be swapped.

Now plug the ailerons into port number 5 (I think on the ar500 it's labeled Gear or Aux). On your radio use the mix feature. Use the aileron channel as the master and the Aux 1 or Gear channel as the slave. It'll go into more detail than I can in the instruction, but this should help guide you in the right direction.

P.M. me if you need more help