That's right, there's no huge or massive transport. It's not that I forgot when I made Last list, but it has never been in the list. So far AFAIK no mod includes any of those sizes. I would be a good addition to the list though.
I just finished all extra sizes for the Yuuzhan Vong! (Unless more sizes such as a huge transport are added)
http://se4kdy.cyberwars.com/races/sw-yv