How to change the mass of a default drone


I am trying to modify the iris.sdf file to make a heavier drone. So, my thoughts are that just by changing the mass of the drone,its inertia, the motor constant of each one of its motors, and the maximum RPM allowed, this should work, but it is not so.
I am just trying to make it take off from the ground, so I guess the main problems come from the thrust generation, since when i change the gravity to low values in gazebo, there is no problem.

Does anybody know what it is left? @LorenzMeier @Jaeyoung-Lim