Im in the process of making my overflows, Im a very DIY person and im not at all scared of drilling glass, i also have several old 10 gallons to practice on. I dont have a return yet, im trying to figure all this out before i go and buy any pumps or bulkheads. I just need help figuring how many GPH to put through my sump and the size holes i need to drill, bulkhead types and size and what kind of return pump.