Is it possible to add one rotor to a zone? I have a system with 8 zones. Most of these zones have 4 rotors although a few have 3. I would like to add one rotor to a zone that has 3 rotors on it. Can this be done and is it something that I, a homeowner, could do? I'm thinking I could just tap into the end of the line and dig a trench (would only need to be 6 ft or so) then add a rotor. Is it this simple or is their more to it or something I'm missing?