The ideal solution depends on just how the roof is laid out, where it is practical to run pipe, etc. With the minimal information you gave, the solution you have is as good as any. If the roof imposes constraints that make your current solution difficult to install it might be worth exploring other options. If you understand how to lay things out to match your diagram and aren't wasting a lot of pipe, then I would go ahead and do it the way you have it drawn.