Not only is Meridian's suggestion not implemented, but apparently the way the game calculates this stuff is still totally wrong.

Warthog MkII (200cu) + TungTaur (300cu) = Too big for a Trident (500cu) ???

I saw your Ticket on that, I'm letting Ray respond because I have no idea why that might be the case. I did change the numbers to reflect the Suggestion, back when I posted.

Not to be super obvious, but you're sure there wasn't any stray cargo using up space, right?

This is all pretty new, in terms of feature-set, so a certain amount of bug-fixing is going to be par for the course.

Positive there wasn't any cargo using any space. We even tried it with two small fighters and 400cu of cargo. Tridents are just bad at math.