We have the same goal here. Though we only have carcass weights for our birds I thought I'd share our experience with the Delawares incase it's helpful in some way.
This was our first year trying the Delawares for meat. We purchased our Delawares from SandHill Preservation Center. Unfortunatley, the chicks were sent to the wrong place and several of the chicks died. Of the 5 survivors we only had one hen and she seems on the small side to me.
We kept the largest rooster and butchered the other 3 at 18 weeks. I wish I would have let one go till 20 weeks because the rooster we kept really put on a lot of growth between 18 and 20 weeks. The 3 roosters weighed roughly 3 lbs. carcass weight. Of the breeds we purchased, the Delawares grew the fastest and the Silver Laced Wyandotte/Brahma crosses were really fast too. The rooster we kept is now 23 weeks old and he is pretty big. He started his "rooster" thing about 1 to 2 weeks ago so butcher time for these guys seems to be around 20 weeks from our limited experience from this hatchery.
Next year I'll be hatching eggs from the Delaware rooster crossed with the following hen breeds Delaware, Range Sussex, SLW/Brahma, and Chantecler.
You may want to try crossing breeds for hybrid vigor if your main goal is meat. If you can get a good source for American Bresse they do grow quickly from our experience, faster than Delawares but we didn't like them as much. I would definatley try them again if I could find a good source for birds.
