Lay the parts out to figure out each component's placement.

Determine the orientation of the main controller.

The "DB port" side must face either front or right side.

During software configuration enter the main controller's orientation.  This is important for the IMU sensor.

When deciding the orientation of the main controller remember the direction the DB15 cable will have to travel to.  Do not bend it so much that it causes cable fatigue.

Measured the holes on the helicopter's frame and drilled on the upper plate of the main controller to match the L-brackets that will be used.

Be careful when drilling the holes.  Use a "drill-stop" to prevent damaging the main controller.

Or remove the controller from the housing.

Initial plans were to make some elaborate mount.  Then realized "What for?". 

Readily available L-brackets from local hardware stores will do the job.

L-brackets mounted.

Used long-nose pliers and an open wrench to hold the nuts in place in between the upper plate and main controller.

Here's the Main controller mounted underneath the helicopter's frame.

The KDE bottom bracket upgrade for the 600 is perfect to securely hold the main controller. 

The existing holes on the frame were filed larger for the M3 screws.

Another view of the Main controller installed.

NOTES:

- Do not install the main controller inverted or in any other orientation.  Make sure it is leveled.

- The main controller should be installed as close to the center of gravity as possible.  For example right underneath the main shaft.  This will lessen the amount of airflow caused by the main blades.  Remember the main controller contains the barometric and inertial sensors.

- The main controller should be placed away from any heat sources, electromagnetic sources and servos. 

- Remember to leave enough space where the USB cable plugs into.  Access to this port is required during software configuration and future adjustment of the main controller.

The SD card is inserted with the contacts on top.

Make sure the SD card is seated.  To remove push on the card.  The SD card port is spring loaded.

This is file format of the data recorded in the SD card.

Don't bother trying to read it.  If some assistance is required with fine tuning or trouble shooting then send the file to DJI and they will analyze it for you.