unstable force obtained from Contact Sensor

Hi all, I'm using the contact sensor plugin in ros (libgazebo_ros_bumper.so) to get the contact forces from gazebo. It works very well for the contact positions, but it's extremely unstable in the force computation. Basically i have the same problem seen [here](http://answers.gazebosim.org/question/6172/contact-forces-oscillating-for-a-basic-box-shape-on-ground-plane/), i tried adjusting those parameters, but without success. I also tried averaging the last 50 samples, but the result is still highly oscillating. Someone knows how to get a reliable contact force? I'm using Ubuntu 12.04, Ros Hydro, Gazebo 1.9.6