missprissy post her detailed experience with jumbo cornish X well i would like to know when should you "harvest" these chickens for maximum meat amount and quality
It's a matter of personal preference. The longer they go, the bigger they get but the more apt they are to up and die of fatal heart attacks and strokes.
We did our first-ever batch at 13 weeks. We never lost any to disease, heart attacks, or leg problems. They were huge. I had an Amish guy and his sons process them and he called them "almost turkeys". The only drawback for waiting that long was that they were slightly tough. Next year, we started at 8 weeks and finished at 11 weeks. No problems noted. They are definitely 'firmer' than store-bought, but then again we didn't soak them in brine like the big guys do. At 8 weeks, they're about a normal sized roaster. This year, I'll probably start at 7 weeks for broilers and finish at 10 or 11 depending on how ambitious I am. We'll have about 150 to do for this year's first batch and maybe two more batches after that if they market OK.