first the 06 and 07 had lighter cranks than the 08 and up, the intent was to make the power more linear. so you probably can't go much lighter.
going big bore will make it rev slower and the stroker will make it rev even slower, it should make huge torque. I have a 100mm Athena big bore making it a 490 and a stock 450, in my opinion the 450 will kick the 490's a$$, the 450 does have some mods.