Ah hell, comm lag's a real sum'bitch ain't it? Forgive the delay, Belter. Let's get you sorted.
You're absolutely in the right to use the Tier 3 bird for Tier 4, as that was our intent when we published the game--though it's no small amount of consternation to hear that the rule didn't get proper immortalized in ink and such. I think there's absolutely room to decide that it's different in your corner of the Belt, if you want a more even spread, and I won't blame you none if you do.
But the Consolidation left a lot of Military Hulks adrift, and so the bigger the bird, the more likely it is that it's Military.
Chariot, out.