you talked about poor handleing on the ground with lack of rudder authority and wheel authority. A possible explanation is if you have the plane pointing slightly up while it is sitting on the ground you create a positive angle of incidence, which means that as soon as you put any speed on the nose wheel get light because it is trying to lift off a little. Since there is no weight on the wheel it loses effectiveness. at these low speeds the rudder does not have enough airflow yet to be effective. test by applying a little down elevator at the beggining of the takeoff run and see if the handleing is any better. if this is the problem you could adjust the attitude of how the plane sits on the ground or just remeber to press a little down stick on the beggining of the takeoff run