Your takeoff roll is actually not all that uncommon -- or at least I have seen that several times on some of the UF's. On mine I have a separate takeoff rate with the steering rate turned down very low. This rate comes on when I have the gear down and flaps deployed otherwise set to full rates for Taxi. Also, lots of people use a cheap gyro just on the steering channel and that really helps take the wandering out of the equation. I don't use one on my Flash but do have one on my Comp Arf Viper which has a huge tail fin and can wander on takeoff roll with big cross winds. Takes that problem completely out of the equation.