I'm flying an Eflite CP 4-in-1 in my Walkera Dragonfly 4, using a Hitec Flash 5 transmitter. (it doesn't need CCPM)
I needed the positive Expo to overcome the sluggish response of the heli.
Any aftermarket transmitter will need 120 degree CCPM mixing, as wall as the proper shift.. negative, for the Eflite receiver.
I'm using a Berg 7-channel receiver in my Blade CP, with the Eflite transmitter.