Algodoo

If you make the ball small and dense (radius=0.05, density=1000.0) and use the Large Amplitude Pendulum formula then g comes close to the expected value. I used a 3m long remote hinge pendulum with radius=0.05, density=1000.0, and starting angle=15° and calculated g to be 9.799 m/s^2.

Here are some ideas:
1. Use a stiff spring for the pendulum string. A spring should add no mass.
2. Attach the spring to the center of the bob.
3. Make the bob small and dense.
4. Decrease the size of the initial angle or use the large angle formula.
5. Glue a large low density bob to the small one.

Sure your scene might not look as good, but at least you will get accurate results.

Thanks, Will Try and Update...

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