I think 7 channels is enough
elev - 2
rudder - 1
alieron - 1 (reverse Y ) ?
flaps - 1 ( reverse Y ) ?
throttle - 1
gear - 1
You will not need a reversing 'Y' for flaps, you want them to move in the same direction i.e. both down at the same time or both up at the same time.
Why 2 channels for elevator??