Of course above all the birds can really throw a monkey wrench into even the best laid plans.
No matter what you do good records are the most important thing.
One of the things that I think gets over looked when comparing studies etc. Is how the study is conducted and what the study is trying to tell us and ultimately comparing the study to what we are trying to do. There have been several attempts to study the differences between pasture raised birds and barn raised birds and most of them have difficulties getting information to compare because the method are so different. Your birds will be raised your way the only true way to know if you are making progress is comparing year over year of carefully bred birds.