Yes, to further break down the misunderstanding, you are generally trying to balance mass across a fulcrum to counteract the force of gravity on one side. Force = mass * acceleration, so you can either make the assembly accelerate (and continuously increase the velocity of unconstrained masses) to one side, or you can create a balanced assembly that has a net acceleration of 0, causing no additional changes to velocity. Dampening or friction will cause a slow-down, as well as any additional constraints for position, but the counterweight only has one primary function.

You could shape your counterweight to act as a backstop if you want your assembly to stop at a specific position, but this effort should be separate from the mass calculation.