They are all about as delicate as you could imagine something made of card stock being. At the same time, they are extremely light, so there is never a lot of worry about them collapsing under their own weight.
Most of them have some form of reinforcement inside, such as wooden dowels and tongue depressors (The Maelstrom has a few solid parts along the fin struts), but they are all mostly hollow inside.
I'm extremely lucky that I work somewhere with a decent color printer. Mine at home isn't that great either.