I've come to the conclusion that weight has little impact on grip and corner speed. Weight does affect some things like acceleration due to the lower hp/weight ratio. Extra weight CAN also how change quickly you transition from left to right and right to left, but it's not the only factor.
I can ride my 590lb VFR at basically the same pace I rode my 425lb CBR. Ultimately, I was a bit quicker on the CBR, but not by much...that probably has more to do with the amazing front end of the CBR rather than the weight difference.