Transmitter
We use the Fly sky FST6 model transmitter
Fly Sky set up
Also Taranis Q X7 has worked well for us
Rudder Servo
We use this digital rudder servo that we find turns the rudder very fast Hiteck HS-5646
Standard Digital HS-5485HB also works well with the D4
Sail Winch
290 EF has been most effective winch for the D4
Waterproofing electronics