down in the spout

To give help in getting into and out of the cottage, over the years I have constructed in two places a deck about 8' x 8' or so. One of these is in the corner of the large screened porch and the outside from kitchen window, so the "valley" of the metal roof guides prodigious amounts of rainwater onto the deck and the water also splashes against the exterior wall siding (stressing the paint job). I have contacted a contractor and requested an estimate. I want the big (5-inch) gutters and downspouts due to the heavy rainfall along the shore - Chesapeake Bay. We are planning to go down - before the beginning of November, 2014.