Remove the best type of weight from your sled that you can...
Rotational mass.
We removed weight from the furthest point from center, giving the best reduction of weight on the flywheel. .35lbs off the engine is huge. This modifiction is great for on and off the throttle use. Winding trails, hill climb, racing, and technical backcountry riding.
if choosing core exchange, new flywheel will be shipped upon receipt and inspection of your old one.