I found the cabin bit much easier than i originally thought it would be.
I just hung around near the stairs, blasting everything with my arsenal of guns =D
The way my friends described it, it sounded way harder, like more enemies, longer duration in the cabin...
Did anyone notice that you can push the book shelves and other stuff in the cabin, which you can push over the windows and door?
10 - Supply Depot (1)
13 - Barracks
15 - Marine (1)
16 - Orbital Command + Supply Depot (2)
16 @100% Marine (1) - Command Center (2)
21 - Bunker (1) + Barracks (2) (3)