This is an update of what I have been seeing with my Breese/Cornish x cross. I have been feeding my 12lbs rooster and 2 hens layer pellets, about a 3/4 pint mason jar 2 times a day. They look healthy and did not gain anymore weight. I notice that my rooster started sleeping on the 1.50 foot high perch. He used to sleep on the ground, but it looks like his food ration toned him up a notch.
I lost 2 F2 hens with white legs recently. It looks like they died from being over weight. They weighed 10lbs which is not good. I started hand feeding my flock with pre portioned rations, instead of filling their all you can eat automatic feeder.
I processed some F2 and noticed that they were packed with fat. I have 5 F1 hens and 1 rooster left from my F1 batch. I will process all the F1 hens and breed my 12lbs F1 rooster with white legs back to his F2 daughters with white legs.
I kept a fat F2 rooster with dark steel blue legs, to keep my own Breese line active. He doesn't perch, but I think he will with his new diet plan.