Missleman is right on the money. Balance your plane with the tank empty. If you balance your plane with the tank full then when the fuel is used up the plane will become increasingly tail heavy. There is a saying that a severely nose heavy plane flies poorly, a tail severely tail heavy plane flies once. You don't want to be landing a tail heavy plane at the end of your flight, especially if you are out of fuel and making a dead stick landing. The little bit of nose heavy that you get from a full tank is no problem at all. Always balance with an empty tank

Ken