ISA Browns Roos vs Hens
You do realize that because they are a cross breed, they don't breed true and you will not get sexlinked chicks when you breed the roosters to the hens, right?
Sexlinks are a cross between to different breeds with the intent of being able to easily sex the chicks at hatching. It only works for the first generation crossing. The resulting chicks have what is called 'hybrid vigor.' The males grow a bit larger and faster than either parent breed and the pullets are exceptional layers, but those traits don't carry over to the next generation quite like the initial crossing.