I recently flown a F-15 which had aleirons mixed with the elevons. The plane had a "strange" feel in turns and nor the owner or I knew what was the cause of this problem,,, flew it twice, checked servos, bats, everything but the problem continued. After some head scratching I found a setup problem in the radio: the elevons had 25% of expo but the ailerons where incorrectly mixed directly to the aleiron stick, so they didn´t had expo.

The difference with the correct mix was visually imperceptible at the surface movements, but they where huge on the F-15 handling, that handled as good as it should after fixing this.. so the moral is to be extra careful in the mixes and throws if you are going to do this setup.

Enrique