hi i keep racers too, dont pay alot for them to start with ,try and get a couple of pairs , that are from the same person, and that the birds are the same family but are not to closely related,then you can swap them around,then you will have a little family line to try,give em a few seasons to gel and if no good get shot and try again,your shed is a nice size,but you might find it easier to split it in half, would make management abit easier