I have a deck that has sunken a bit in the middle, so the drain pipes in the corners do not get a large puddle in the front center. I have tentative plans to cut the base of the wall at the center and install another drainage pipe. I would have to grind out about a quarter of an inch of the deck surface next to the new pipe so that the puddle will drain satisfactorily during rains. However, I have been told that fiberglass surfaces (the deck surface is some kind of fiberglass) are a big problem in this regard and I shouldn't do it. Does anyone have any experience regarding this situation?