Spent some time tonight lightening one of the two spare flywheels I got.
Managed to get 1/3 of a pound off it. You could possibly get a bit more but that's all I dared to take off. Weights are in the pictures. I couldn't use my dope fink scale because it would only measure grams or ounces.
CO

I like the idea of this. Looks like you can also trim off the outer lip edge of the 'bowl'. Also don't forget you can likely trim the starter ring gear, pull start basket, or remove something there entirely. Make sure you balance that flywheel as best you can.