We butcher our birds btw 4-6mos and get processed weights of an avg of 4.4-5.5 lbs. I don't know the bone to meat ratio vs other breeds, but 1 bird is enough to feed our family of four.I had Sandhill white Giants for years (I've crossed my white naked necks with them now, really love the naked necks, great layers, best meat bird for heritage IMHO, small at when I process when the roosters start crowing I process the cockerels and pullets that don't fit into my breeding program, they are about 3lbs dressed but very nice. Should be bigger now though with the giant cross(haven't processed any yet) Half the feathers easy to pluck, and NO hair to singe off the skin not even on crosses) one thing I always heared when I had the Giants, same thing with Brahmas I'm sure, that they are hogs, too much to feed them. Not in my experience, had a very mixed flock of many breeds when I had them, and had kept them separate during breeding hatching purposes. I found them to eat way less than everyone else. I think it's because they are so docile laid back, not on the go go go like some other breeds. And they, and I'd say Brahmas also, say takes too long to get to processing size. BS I say, yeah they take nine months to a year to get to their potential of 9-13lbs, but younger just as much meat or more than all other heritage breeds. Bigger bones but weighed more, more meat at when I usually cull about crowing age. The giant birds make great dual purpose, my giants laid as good as everyone else also, and where more apt to lay into winter without extra light.
And I had my Giant rooster chase off a fox one time, according to DW and my oldest DD's boyfriend who were home at the time, watched him beat the crap out of it pecking and spurring as it was running away. I did lose when of my best GJ hens but at least the fox had no chance to eat it.
We rarely allow the birds to reach beyond 10mos of age. Although they still make incredible soup and pulled meat for sandwiches, I have found them to be too tough for frying or roasting, hence the young butchering age.
We are currently overrun with eggs. Our 8 hens are producing 6 eggs a day so our neighbors and friends are sharing our bounty.
The 1 bird we lost to a predator (fox) was a 10-11 lb 11 month old rooster. He has been our only casualty since we started keeping chickens and that came before we got our dog (family pet not a guard dog).
Our current breeding rooster allowed to free range with the flock just turned a year. He's only 10 lbs but he stands nearly 30" tall. His height makes him look even skinnier. His father was 28" tall but had a live weight of over 12 lbs.