You can either use two aileron channels, or just a 'Y' lead into one channel.
The 'trick' is to ensure you mount the servos so that they do work in opposite directions, whether from separate channels or a 'Y' lead.
Best way is to lay the servos out as you expect to mount them in the wing, connect to the receiver and see with way they move. The output arms need to move in opposite directions. (See picture).
If you mount the servos vertical, (they are shown on their side in the picture), you could just attach the output arm to either side to give opposite rotation.
Separate channels may also allow yo to use the ailerons as flaps, (both going down, while still capable of being ailerons), it will depend on your Tx's capability.
Sounds like a nice little project.
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