Ol Grey Mare… That is a very interesting feeding concept/structure you have in place. When I read your very nice response to the OP, I had to take pause and think of my on strategy. I will have to take this method to heart, and contemplate using your method. I have just 'fell' into a lay mash/pellet mindset and not really thought of feeding an all flock or other such feed that does not have the calcium included, and just offer it free choice via oyster shell.
I am always up to finding a way to improve my management system(s). Over time I have refined my backyard operation, to a point that I seldom change or bump into a significant improvement for my birds and style. Home runs, such as horizontal nipples, just don't come along all that often, but I suppose there are many (I hope) tweaks to my bird keeping that can still be improved. Next trip to town I will have to take a look at the offerings for a diverse flock. I am delighted to have found a new method to research and even give it a try into my birds.
Always grateful to learn and to try something new.
RJ