Your best bet would be to get some fishing weights and keep adding until the clock works correctly, then add a little more for stability. The weights are not too critical.
The pendulum is a different matter. It is this which determines the accuracy of the clock. I would start with a rod about 6 inches long but with an adjustable weight on it. Move the weight closer to the clock if the clock loses time, and further down the rod if it gains time. Sooner or later you will hit the magic position.
Colin, December 2007
