I recently put a GYT-R 8 oz flywheel on my '03. I've only had one day at the track since the install, but I already know I like the change. The stock '03 power was manageable, but still a handfull in some situations, especially off road. I figured the 8oz would be a good happy medium, not so heavy as to take all the "fun" out of the power, but heavy enough to make a noticeable difference. so far I'm really happy with this weight. The motor feels a lot more "426ish" which in my opinion is a good thing. In saying this I don't mean it has less power, but it is smoother and more controlable. When you grab a handfull of throttle, the response is more predicable and you are less likely to break the rear end loose in corners. The other benefit I noticed is the smoother power doesn't tire you out as quick. I could ride much longer without getting tired. So far I really haven't found any negative aspect of the new flywheel and would highly recommend it for anyone.