i have used a Delta Mix Modul
at one Input from this Module comes Aileron Signal from the Ardupilot
and for Flap Mixing i have connect the Receiver out to the second Input from the DeltaMix
(the Deltsa Mix is normal used for Delta Planes, aileron and elevator at once, one input at delta mix makes the aileron function and the other the elevator Input)
Yes, it is possible directly with APM. Look at the wiki differential aileron page.