they look great mate the only thing i would say is maybe its in your plans allready hope u dont mind me saying is too put some rope accross the top of the roof mabe about 4 to 5 lines in line with the roof edge mine go about a foot in height on the edge of the roof (hope i explained that right)
as u know when there racing they will land on roof then to trap and they can play on roof for while if the ropes are there they have to hit landing board :-/