I"m sorry. I have raised BBB and BBW and bourbon red and other heritage breeds. THe BBB is a "breed" selected for the VERY fast growth to a large market size. WHen it passes the 4 month mark, when it should be butchered , it will keep growing. ANd yes the legs are not strong enough to hold up a 50+ bird. Just too much heavy breast muscle for the legs to support.
My BBW just sat at 5 months old and at 50#-- a trip to the butcher is a merciful end.
SOrry.