Don't forget, per earlier books, ships can't go to lightspeed too close to a gravity well, which is why the Empire had ships designed to simulate gravity wells.
Wasn't it explained elsewhere that it wasn't really an inability of the hyperdrive to jump, but rather that it played such hell with the navigation systems that you'd have to disable multiple safeties, bypass computer nav and manually pilot the ship in a situation where manual piloting was so ludicrously beyond the capabilities of even a perfectly tuned in Jedi that the only possible use was a short, line of sight jump? (i.e. point, engage, disengage before you ram something bigger than the navigational shields can handle. Thinking about it in terms of an Earth launch, the moon is 1.3 light seconds away, so assuming you only go light speed, can miss every object over, say, a cubic meter in orbits between here and there, don't actually aim close enough to the moon to be redirected by its gravity, and don't burn up from atmospheric friction before the actual transition, you're already way past the point where you couldn't see items a thousand times bigger than you can risk hitting when you were pointing the ship.)
In other words, they're basically saying their computers can't handle the calculations fast enough, but you could try seat-of-your-pants flying, with a huge chance of catastrophic collision that increases by the nanosecond. Assuming any meaningful sort of steering is even possible, since they mention dropping back to realspace to maneuver between hyperspace routes.
Of course, for ramming, most of the above, other than bypassing safeties, is irrelevant; center it in the windshield and mash the gas hard.
Interesting yet vague mention of an accidental hyper-ramming:
http://starwars.wikia.com/wiki/Destruction_of_Pammant
