This a point I've made several times. Dr.D, GYT-R, and other flywheels that add weight by welding a ring to the outside of the flywheel concentrate the added weight at the most effective place on the flywheel; the outside edge. Bolt-on weights necessarily have a center hub area that's used to bolt it in place, and the weight of that portion of the weight does not contribute as much inertia as the mass placed nearer the outside of the part. That often means that a lighter welded weight is as effective as a heavier bolt-on. Additionally, welded weight flywheels are balanced after the weight is added, and there are no bolts to loosen up. I had a heavier flywheel on my 04 that actually de magnatized the magnets then the stator did not stator and it didnt run.