Billet Steel Flywheels?

["Irv Korey" <emanteno@attglobal.net>]

Cambridge Motorsport in England lists "steel billet lightweight flywheels"
to fit the TRactor engine. They supposedly weigh 7.75# without the ring
gear. Does anyone on the list use one of these? Can anyone educate me as to
the potential advantages/disadvantages of this versus an aluminum flywheel?

Thanks much,

Irv