just keep line breeding with them and youll be right. put father to daughters one year then the next put the hens over a son and the next year him over the pullets he produces and so on.
Thanks - good advice. I'm doing precisely that this year - I'm not keeping any of the sons (I don't have the pens! - I know it's a little risky), and we'll see what happens when the numbers bump up.
I plan to bring in standard utility Leggies into the commercial flock and will probably put sons over them; they've got the egg colour I need, and hopefully can infuse the calmness, health, and fertility of the CSIROs into them.