Just to point out, the Hurricane is 6km in length only. Its actually a very slim ship. To compare with the Hecate:

I suspect the Big H5 is a mostly weapons platform. Just thinking of how much space in the ship is completely devoted to gigantic spinal reactors to power its huge weapons leaves me to imagine that the thing has a disproportionately low crew capacity. Especially considering it lacks a dedicated carrier capacity. Maybe... 15,000 crew.
On another note, looking at the nose cannon and the Hecate.... hehe I'm pretty sure no FS Destroyer would want to be in the H5's sight line. Though I'm pretty sure that the Colossus could probably give it a run for its money in terms of broadside beam cannons. On the other hand... I'm pretty sure the Colossus wouldn't appreciate 13 750m long turrets firing 700m long plasma bolts at 6km/s every 1-2 seconds that much...