Flaps
The 6XAS is long in the tooth. There are far better radios out there for the money, like the RD6000.
Flaperons require a servo in each wing, rather than just one in the center section. Most people do this by installing them between two ribs, although I have a friend who used a novel approach in just widening his center servo hole to accomodate both servo. That's probably the easiest approach.