Bone gravity in PHAT

I have a few bones which I would like to simulate but they have too much inertia when my mesh moves, if I just increase the mass that does not help to counteract the inertia because inertia is dependent on mass as well. Is there a way to increase the gravitational effect on certain bones simulated in the physics asset? I have seen this option for cloth simulation and wondered if there is something alike for PHAT. This would apply a counter force which could help. If there is no option for gravity is there another way to apply a force on specific bones or maybe decreese the inertia when moving in the world?