I've searched the threads and am pretty sure about how to make the pikup tube and connections and how to drill keggle but am not sure where to drill hole. I have a Bud keg, how many inches from bottom should center of hole be. Also I have a 1/2 inch drain, threads say to cut 7/8 inch hole. Is that right? I know I have only one shot to do this and want to get it right.