The Dunlap birds put me about three years ahead in trying to get a larger breast. You still might want to get some "meat" pullets (cornish/rock) and use the Sagitta Cockerels from your flock. That (if my math is right) would give you a 37% cornish breast and still get a bird that will free range.
I had to sell the farm in January 2019, I can no longer care for it properly, time for the next generation. Enjoy your good life, I have.
The choices with the flock late last summer were for consistency in color, the dark mahogany that shows up is beautiful.
yes , February 2017 chicks, bought 50, kept 12 pullets and three largest cockerels.
used the largest of the cockerels as my breeder. I then hatched over a five week season in the spring of 2018 and processed those as they began to crow.
I am not a poultry judge, that being said they looked like the chickens from the prior year that I got from the hatchery, and grew just as fast, no problems with 25% Cornish in their breeding, Cocks were fertile, hens laid well, shell strength was good.
one you might try (someday) is the Sagitta cross available from Dunlap hatchery in Idaho.
http://www.dunlaphatchery.net/buhl80/Dunlap.aspx?codeid=SAG
https://www.backyardchickens.com/threadloom/search