In my backpacking days, I always used a hammock: I lived in Pennsylvania, which is very rocky, and it was hard to find a rock-free spot on the ground big enough to pitch a tent. With a hammock, I could sleep comfortably off the ground any place where there were two trees close enough together.
But there are a few things to keep in mind if you want to use a hammock in a van. You may have a limited number of places where you can safely attach the hammock. The weight will place a constant strain on whatever it is tied to, and some parts, such as door handles or cargo gates, may not be able to handle it. The hammock itself is also under constant strain and friction, and it won’t be unusual for the ties to wear out and suddenly break in the middle of the night, dumping you onto the floor.
Hammocks are also not particularly good for cold weather. Because they hang off the floor, there is always lots of airflow underneath you. In the summer, this is nice because it makes you cooler. But in winter, it will rob you of a lot of heat. As a general rule, I view “hammocks” as potentially useful in summer, but not so good in winter.
