Hi, we bought the M600 Pro with a D-RTK.The D-RTK came with the Mounting Bracket Spare Part NO. 6. As it turns out this is for the M600 and not for the M600 Pro.
The mounting brackets for the plate should be screwed on top but the extra GPS Compass Pro's occupy the holes for these brackets. Also the plastic cover is bigger to fit the additional A3 Pro's and uses holes meant for the brackets.


Before I start drilling, cutting and filing I ask you.
Is there a kit from DJI for this? I could not find it.

Here is a picture

http://forum.dji.com/thread-95751-1-1.html

Thanks Quadrocopter,

I modified the M600 kit to fit the M600 Pro. Didn't turn out too bad.
I seems you had the right hardware kit. I asked DJI support if it existed. All they replied was "that there is no Matrice 600 Pro- Upper Expansion Bay Kit st present on DJI Online Store."

I'll post pics of the modification later.