Fred Zillich's leghorns lay very well. I got RC whites from him, and RC dark browns (he has other colors too).
The whites are a bit more seasonal, the dark browns more year around steady.
The whites matured a bit faster than the dark browns.
The whites have eggs a tiny bit larger than the dark browns, but both lay a good sized egg, only a bit smaller than a production white Leghorn.
The dark browns are the most "predator aware" chickens I have ever had, super skittish, but they still consistently lay in the nest boxes.
I only very, VERY rarely let my chickens out to free range, since I have way too many predators, but I think his dark browns would be stellar free rangers.
I haven't had any medical issues with any of his stock.
So, they will not lay as well as production white Leghorns from a hatchery, and their eggs will be a bit smaller, BUT, they do lay very well, and unlike the production White Leghorns that I have gotten from hatcheries (who are prone to prolapse and vent gleet), I have had zero problems with the dark browns.
Also, the dark browns should be excellent free range foragers.
They sound like a great option for us!
Does Fred have a BYC account or email that you know of in case he doesn't see my fb message?