When I land my plane and just as it slows down enough for the tail wheel to touch down, I lose all steering ability. If I push the plane down the street I can turn it fine and also while the tail is still in the air my rudder is able to turn the plane just fine. Something to do with certain speeds I guess? Tail wheel need to be bigger perhaps? Or do you think the main gear is out of alignment and it is magnified at higher speeds and the tail wheel can't overcome the tendency to turn?
The plane in question is Great Planes 1/4 scale Cub

Edit: Also, I have flown tail draggers before, its just this one giving me fits.