RE: Dx6i Dual Aileron & Flaps Setup
One of the problems you run in to with a lower end radio is that the programming is more limited. The DX6i is a nice radio, but mixing is more limited than the DX7, 9303, and 12X.
There is another thread on just this subject that you might want to search for.
I do not have a DX6I but I have helped train new pilots who had purchased that radio and I am very familiar with the programming options available in more advanced radios like the 9303.
The Flapperon program is a common method to put a servo on each Aileron half, plug them each into a different channel, and mix them so they both work when you move the Aileron stick. It also allows the Ailerons to move down when you move the Flap Switch. Many people just use the Flapperon program to mix the Aileron servos on Ch 2 and Ch6 and they turn off the Flap component.
If you have an aircraft that has functioning Flaps, you want to connect the Flap servos to the Flap channel, connect the right Aileron to the Aileron channel, connect the left Aileron to the Gear channel and use a Programmable Mixer to mix Ch2 and Ch5 with the Master being Ch2 and the Slave as Ch5. You do not use the Flapperon program at all.
With only 6 channels, those are your only options.
For the Flaps, you may want to consider the JR Matchbox, instead of a Y Harness. The Matchbox allows you to connect up to 4 servos to one channel and adjust the Servo Direction, Neutral, and End Points, for each servo. This will allow you to Match the two Flap Halves so they move together evenly, without having to make many mechanical adjustments.