The ship is big, but the hitbox is huge! Some quick testing showed the hitbox to be wider than the wingtips of the Juggernaut, and somewhat longer than the overall ship as well. At extremes a shot can still hit the Juggernaut when it is a Large Train's length wide from the actual hull.
Also, the weapon arcs may be restricted by their hardpoint positions but I haven't had chance to test this first hand, I'm just going by another player's words here.