As I understand the elongated shape has only been determined based on the light curve. I'm guessing this assumes no big changes in albedo along the surface. It

As I understand the elongated shape has only been determined based on the light curve. I'm guessing this assumes no big changes in albedo along the surface. It might actually be a much more round object with one light and one dark side. Iapetus is an example of an object with such coloration.