The eleventh flight appears for one of two reasons; either two feathers growing from one follicle or an extra follicle. The extra follicle will increase wing length and thus alter the leverage. This could be the only problem, however nature has a knack of balancing these things. I think the most important things to breed into our distance candidates are the un-seen traits; those traits that the likes of Derek has in his loft of birds. A desire to home, to do so quickly and to appear through all difficulties. How do we find those traits? Send them, then improve ourselves!