Hi Roger,
Just completed the radio install on my new Silver Spit. Complete with Electric Retracts.
The box to the right is a Power save from SM Services, with this you power up your servos with its own power souce and power up the RX (2.4) with its own. You can use 4.8 or 6 v.
Here is the link:
http://www.smservices.net/acatalog/On_Board_Units.html Terry and his lovely wife are great and very helpful.
Also ran up the motor.
DB