depends on your tx
you could set up the top ailerons on channel 7 and 8, run the bottom ones using channel 1 and then mix 7 and 8 off of another channel such as 6 to give you flaps and channel 1 to give you your ailerons, that's the only way I think you can do it, will take 4 mixing funxtions though.

Sorry I misinterpreted your question.

Why do you only want to use the top ailerons, is that what the manual says?