You need at least 6 for a heli.
A Heli Tx will allow you to adjust the throttle curve to collective better.
So you might look into a Heli tx

To convert a Airplan TX into Heli all you have to do is remove a little brass tab
or visa sersa..put the little tab back for Fixed wing. it'll get you started in learnding
to hover, but you would probably want better throttle curve mixing when going to foward flight or 3D

The click feel when you use the throttle.