Burtz vibrations

[sr325]

Hi Guy, I recently finished building my Burtz engine and it is not nearly as smooth as I had hoped. Ive got even compression at close to 90 lbs on all cylinders, I had the flywheel and clutch Balanced and the engine pulls strong and evenly through the rpms. Vibration is worst when engine braking. I understand that these engines can never be perfectly smooth. But how can I determine if it is vibrating worse than it should? Thanks for any thoughts.