My pond is about 3/4 acre in size. It is just about full. We have the lowest point dug down a bit and are ready to put in the drainage/culvert pipe. My buddy said to get a 12 inch x 20 ft pipe. I looked and it looked huge in diameter. They had an 8"x20ft and that looked more practical. What do u think? The pond is fed by a good amoumt of runoff so when it rains hard it drains well but It seemed like the 12 was a bit big... Opinions?