I did not drill a hole in my return in pipe in the DT. I used locline to position it to where it will break the siphon anyways. The hole is not full proof, because of algae, and snails or anything else that might clog the little hole. You should look into finding a cheap 55 gallon tank on craigs list, and make your baffles to the height that your sump will have 5-6 inches of of space to fill up if the power goes out. I can point you to a great glass shop in Mboro that will cut you the baffles for really cheap.