WarlockLord said:Your ship is armed with 4 ballista. Use DMG rules, except substitute airship sailor for siege engineer.
OOC: Siege Engineering skill is typically only used for Heavy Catapults. The Ballista is just a size Huge crossbow that gives medium-sized creatures a -4 penalty to hit (plus, presumably, non-proficiency penalties if they're not proficient with Crossbows)
"We appear to be outgunned. We've got the lead, let's use it."