Maximum value of sdf <maxRotVelocity> parameter

Hello everyone.
I am trying to modify the iris.sdf to make it heavier. I know there are similar issues about this topic but no one answers my question. I want to make it heavier and fly it (in SITL) in an environment with less density. According to my calculations, the drone requires for hovering (with a motor constant of 2.5e-06) 3000 rpm per rotor, but the maximum achievable value of seems to be near 830 rpm.
I have reached the same conclusion in different ways, by increasing the gravity acceleration until the drone canโ€™t even take off, and by taking the to higher values.

Does anybody know how to change this limit?