My transmitter (Hitec Aurora9) has differential aileron setup and I will check how did I make my setup.
Hangar 9 recommends
[TABLE="width: 99%"]
[TR]
[TD]Aileron: [/TD]
[TD]5/8 in—up; 1/2 in—down[/TD]
[/TR]
[TR]
[TD]Elevator:[/TD]
[TD]7/8 in—up/down[/TD]
[/TR]
[TR]
[TD]Rudder:[/TD]
[TD]1 ½ in—left/right
[/TD]
[/TR]
[/TABLE]
Scale ailerons do not correct this problem (have them on my cub).
You have to put a little rudder and elevator to compensate, or to mix it with ailerons.