Her low freeboard allows for such heavy cannons because they're lower to the waterline. The crew also keep the lower gun ports closed unless going on the attack as would be found with most armed vessels of the 17th and 18th centuries. Dutch warships were also relatively small to medium-sized and shallow on the draft to defend the Netherlands' shallow coastal waters. Heavily armed, their galleons frequently carried both 24- and 36-pounder cannons to be utilized in their favored tactic of close quarters ship combat (typically within pistol shot range) that focused on shattering the hulls of their enemies. This is clearly shown to be the preferred tactic of the Dutchman's crew in At World's End as they attack the pirate fleet where they employ rapid surprise attacks featuring powerful broadsides in close range to sink the opposing ships. It has been noted in the Complete Visual Guide that the ship was a gift by Calypso, which Davy Jones had captained for a century prior to the events of the films which are set around 1740. This would place the Flying Dutchman right in the prime of the Dutch Republic's high watermark for their global naval supremacy - clear evidence for her highly powerful armament.