Whatever dual purpose birds you get, you're really not going to get a carcass much larger than your RIR were. Laying hens just don't make nice meaty carcasses. If you could handle a lower egg production you might look into the slow meaties like Dixie Rainbows, etc. Some folks have had good luck holding some hens over as layers, and they'll have a nicer carcass. They won't lay 300 eggs a year, though. There is no breed that will do both.....