Drag RigidBody Script with NO Springing

I've tried all sorts of numbers in the DragRigidbody script variables, but I'm just banging my head on this one (sorry if it's silly). I want to pick up and drag an object, but without any "spring" or swing (in essence I would like to use a Fixed joint to grab it but apparently that kind of joint won't work with this.

How can I adjust this script so the object doesnt swing around and just stays dead on the mouse?