hmmm some people recommend not lightening any flywheels due to the structure of the wheel being weakend and also the very accurate balancing that needs to be perfect or you will be called stumpy for the rest of your life. personally id like to lighten my flywheel but havent researched the idea enough to see if it is safe or not.
ps: stumpy is the name you get when your backyard lightened flywheel isnt balanced perfectly and cuts your legs off when it comes off at 8000rpm.