Just going by whats written up in hanger 9's manual fr using 7 channel.

Radio Equipment Requirements -
7-Channel Receiver
The following items are recommended when installing the
7-Channel AR7000 receiver (SPM6070) in your aircraft:

DS821 Digital Sport Servo (6) JRPS821
(Note: Only 6 servos required for EP version)

DS821 Digital Sport Servo Reverse (Flap) JRPS821R
RT88 Retract Servo (2) JSP20080

3-inch Servo Extension (2) JSP98100

6-inch Servo Extension (2) JSP98110

12-inch Servo Extension (2) JSP98030

Y-Harness (2) JSP98020

JR Switch, Chargeswitch JRPA004

Receiver battery, 6-volt, 2700mAh JRPB5008

Flaps: DS821 Servo and DS821 Servo/Reverse
• Y-harness (plugged into receiver)
Retracts: RT88 Servo (2)
• 3-inch Extension (plugged into receiver) (2)
• 6-inch Extension (connected to servo) (2)
Ailerons: DS821 Servo (2)
• Y-harness (plugged into receiver)
• 12-inch Extension (connected to servo) (2)