A starship supposedly is built to take thousand-gee accelerations routinely from her own impulse engines. And if warp one imposes any physical stresses, and those have a linear relationship to speed, then a starship capable of warp nine ought to also be capable of flying through a million miles of solid steel as if it weren't there. This being with hull strength and SIFs alone, before shields or anything.
We can safely assume that this at least is not the case. Warp speeds do not operate under normal physics.