I think it is a crapshoot on the breed wether or not there will be problems from their size. I have a jumbo drake and a regular-sized crested hen, along with a standard Pekin mix hen. My jumbo is in excellent shape, but I only feed him once a day with a large area to exercise. Maybe it's the genetics from the parents that give many trouble? Mine came from TSC, so I'm not sure what hatchery they are from... Here's a picture of them.