Well, I don't think the kroozers are accurate in size anyway. Alot of the escorts arent, we know. It is after all a blown up representation of whats on the stem, so its not canonical, I'd think. Maybe the Stronghold is 10 hits because of the tiny amount of crew aboard, I always rationalized the extra 2 Ork hits to lots of crew. But I'd be totally ok with 12 hits on it, it does look quite intimidating.