PX4 SITL Gazebo - customizing the mathematical model?


I’m trying to simulate a DJI m600 hexacopter using Gazebo 7 and PX4 SITL with ROS Kinetic.
So far I have been able to import a m600 3D-Model and get it to work, but I would like the simulation to more accurately mirror how the m600 behaves in reality. The PX4 SITL already contains a model for a hexacopter (the Typhoon H480), so I imagine editing the mathematical model for that hexacopter would be the easiest way to achieve that, but I’m struggling to find the relevant code/files in the PX4 directory.

Has anyone done something similar before and has an idea which files I should look into?