Here is another article that should make everyone happy on the light weight subject please read. so we can get back on topic.
http://www.uucmotorwerks.com/flywhee...heel_works.htm
How does a lightweight flywheel work? Amongst the majority, there are two schools of thought concerning light flywheels. The first is that they do not contribute to power output. The second is that they do. Which thought is correct? In fact both, in a way, are correct.