Most Giant breeders do weigh their birds, and at shows 90% fall within the range for the Breed (Non Hatchery birds). While a lot of Breeders would love to get their hands on a 16-17 pound cock bird, that bird does not fall within the standard for the breed, and is at as big a fault as an undersized bird.Several years ago I bought chicks from a breeder in Florida. Photos they had showed birds that looked HUGE paid a fortune for the chicks. I have BIG Barred Rocks. Males 9-10 lbs females 8-9. My rocks dwarfed these "Giants". I have been at 3 JG Nationals last several years. I have seen VERY FEW the size of Mrs Millers when I was at her place in the 80s. But, although stature is important. Weighing them is as big an issue.
My Cock Birds from last year were between 12-13.5 pounds, and a lot of the breeders do fall in that range. Hens ran 8.5-11.25, pullets and cockerels slightly lighter. At the shows, my birds were not the biggest. A few other breeds have more frame/height, but less mass.