IF you are going to remove weight, remove it at the periphery of the flywheel ONLY, not in the center. The reason it is so thick there is that it is a cast steel piece and needs the thickness for strength. I would not reduce any section of the outer area of the flywheel by more than 20%.
There have been several flywheels that have exploded over the last few years. The most recent one was on Klaus Kleber's car at Nurburgring. All told the damage done was probably more than 10,000 Euro.
Light flywheels accelerate faster, but also are trickier to use. Yours shifts will have to be much more coordinated, as there is less flywheel momentum and the RPMs will drop faster.
The best way is to use a proper Aluminum flywheel. These can be as light as 3 Kilo.
Regards,
Paul Vanderheijden.
