How can I link several rigid bodies together so that when I change the mass for one of the bodies it changes it for all of them? I tried selecting them all and changing the mass, but that only changed it for one of the rigid bodies. I tried CTRL+L to link them but none of the options seem to work for anything physics related. Can anyone help me?
I am not sure if this is what you need but, you can drive the value of one field (ie the Mass field) with the value of another using Drivers.
Attached is a blend file with 2 cubes. A small one and a large one. The larger cube has a driver on its mass field (its will be pink). It takes its value from whatever the smaller cubes mass value is. So if you alter the mass of the smaller cube, the mass in the larger cube will change.
I demonstrate this in the blend file by keying the smaller cubes mass at a value of 1 and then moving 50 frames and keying it at a value of 100. When you advance through the frames the small cubes mass will change and so will the larger one. Though for some reason sometimes blender doesnt display the update.
I am not sure though that just because the interface shows this changes and the driver appears to work weather it will actually get carried across to a running game. But hopefully you can pick it apart and check.
Blender 2.56 - Driver Mass.blend (424 KB)