On my SGT flywheels the machinist drilled out material from the flywheel outer edge according to the balancing, thus making it slightly lighter in the process instead of welding a big plate on.
We used a Ford flywheel as a guide reference to replicate that into the SGT flywheel for my 351W, then final balancing.
We used a Ford flywheel as a guide reference to replicate that into the SGT flywheel for my 351W, then final balancing.