At maturity the heaviest hen weighs 12 lbs, the lightest 10 lbs. Heaviest Rooster was a touch over 13 lbs, lightest was 10.5 but they werent all the exact same age either, but close to being mature ( 18 mos, 2 yrs and up ) .
On another note, it is important to maintain Standards for the breed, they all lay a huge brown egg, although I do have one hen that lays an avg sized egg who has yet to be ID'd. I simply do not incubate or hatch an egg that is out of the realm of normal so that trait can die out.