Sick in bed, so rereading Cinder Spires here, and I got to wondering if it is explicitly mentioned what sort of shape the shroud projects. Barring other information I would assume it's a sphere, but this would mean that the front/back of the ship is more vulnerable to attack (closer to the edge of the shroud), and I don't remember seeing any mention of that.
(Obviously this wouldn't hold for ship with multiple cores).