I've noticed that the official Size of most vehicles doesn't quite match the Target Size Modifiers on page 249 of the core rulebook. I've decided to provide a list of vehicles with what I think are the correct Sizes for each:

Into the Storm

• Aquila Lander: Massive
• Arvus Lighter: Massive
• Calixis-pattern Fury Interceptor: Immense
• Chiropteran Scout: Massive
• Drop Pod: Massive
• Gun-cutter: Immense
• Halo Barge: Immense
• Hephaestus Ore Seeker: Monumental (with a hanger capable of holding 1 Immense or 2 Massive vehicles)
• Land Speeder: Enormous
• Rhino APC: Massive
• Scout Bike: Hulking (no change)
• Sentinel Walker: Enormous
• Venator Pattern Air Yacht: Massive (no change)
• Warbike: Hulking (no change)

Battlefleet Koronus

• Lathe-pattern Shark Assault Boat: Monumental
• Calixis-pattern Starhawk Bomber: Monumental
• Iniquity-pattern Swiftdeath Fighter: Immense
• Iniquity-pattern Doomfire Bomber: Immense
• Iniquity-pattern Dreadclaw Drop Pod: Massive
• Rak'Gol Bloodfury Assault Craft: Immense
• Darkstar Fighter (Kaelor-origin): Massive
• Eagle Bomber (Kaelor-origin): Immense
• Fighta-bomma: Massive

I'm aware that by increasing their size, vehicles become considerably easier to shoot at. However, most of these vehicles have a habit of moving fast, which in my opinion ought to incur a penalty to shooting at them that (for most of the spacecraft and flyers at least) would lower that bonus back down to where it was before I messed with it. I wanted to alter their sizes mainly so that they'd conform to Table 9-9 on page 249 of the core book, 'cause it didn't make sense to me that a Sentinel was Hulking despite the fact that it is the example used for the Enormous category.