I don't think they look at size. Consistency is the thing. Even on both front and back. The binding should be full (i.e. batting goes all the way to the edge). The miters are stitched. Areas are neat where strips were joined. Traditional judges want it hand sewn to the back. From what I've read, the judges will often have a few quilts that are equally well pieced and quilted and use the binding quality as the tie breaker.