Ideal weight for a 29er ?

I was wondering. My friend and I are sailing Laser 4.7s seperatley and decided that we would like to race a 29er. We were not sure what the ideal weight is for the crew. I just looked and it said 110 kg. That is quite heavy so i was wondering how much lighter do you have to be that 110 because otherwise we will have to stock up on the McDonalds!!

Thanks
David