If you plug your gyro gain lead into channel 5, you would use the gear switch and gear channel endpoints control the gyro gain while plugging your governor into channel 7 and use the gyro sense menu to run your governor.
This would give you a couple of gains for your gyro, one for HH, one for normal mode (controlled by the GEAR switch and GEAR TRAVEL ADJUST settings), and the ability to have different governor settings based on the flight mode switch position (if Gyro Sense set to AUTO) or based on the position of the RUDD D/R switch (if Gyro Sense set to RUDD D/R).
The DX7 doesn't have a "Governor" menu as does the X9303, so you have to get creative with the gyro sense menu and channel 7 (Aux 2).
Just make sure under the Input Select menu that you enable AUX 2 as "gyro" and GEAR as "Gear".
The governor would plug between your throttle socket on the receiver, and the throttle servo plugs into the governor. The control lead from the governor would plug into channel 7, you would use the GYRO sense menu to control RPM.
* Making the World Better -- One Helicopter at a time! *