User blog comment:Capt Shruikan/NEW Rank IV Hull Upgrade: StormChaser!/@comment-3328327-20111130155832/@comment-3115143-20111202000840

Rank IV and V upgrades DONT STACK, no matter which upgrade path ye choose (streamlined, cargo, reinforced) WHEN YOU GET A RANK IV UPGRADE, you lose ALL of the extra stats you had and get COMPLETELY NEW stats, which are SET IN STONE for each rank IV upgrade.