Ive just built a small 3DFoamy F15 and have set up elevons (ie elevators do both pitch and role) and flaperons (ailerons do both pitch and role)
...this was achived by mixing channels 1=>2 & 2=>1 (which gave the elevons) and then just connect the right elevon servo to the left aileron servo (via Y lead) and vica versa.
Lots of aircraft use flaperons, but my worry is that since the wing on an F15 is quite deep the flaperons are quite near the back of the aircraft and so when the flaperon goes down (for up elevator) it might cause a nose down pitch - like it would with a delta?
Does anyone know of any model F15s that use flaperons? - Does the full size use flaperons?