The Pirate Thunderhead Bay can hold up to 3 Pirate Thunderhead Fighters, but weighs 70 tons, and costs 5 million form Viking in the Tichel system. Each Fighter costs 400,000 cr. The Pirate Thunderhead Fighter is one of the most combat effective Fighters, but unfortunately they exit the bay quite slowly.
This is far better than getting standard thunderheads. It costs 20 tons less and the Fights are more efficient.