I have a 13 or 13 gallon RCI AL fuel cell. I found I can get a 45 deg. filler neck for it. I had a few questions for the actual hook up of the system. Where can I find a y filler neck? Can the aux tank drain in to the main tank? Will I need a sending unit? The tank is not equipped to handle a sending but I could modify that if need be. IM not certain if the gravity fed will work seeing as how they will be almost even.