What's the problem with a soft hull? A brittle hull would be more unwanted. Wouldn't some softness allow it to better absorb the energy from hits? Plus, mending the hull in place would be much easier if it's malleable. Though it's not as good as a "self-healing" one -- if the cracks could simply join in one of the possible states.
Actually, due to the this thread, I just exchanged the hull of the starship in my book to a soft kind.