Those pursuing #vanlife need comfortable sleeping surfaces; the lifestyle is untenable if you can't get a good night's sleep. However, weight must be minimized for the sake of gas mileage, so a real mattress isn't advisable. What to do?
German manufacturer Froli has devised a way you can sleep on even a thin foam mattress and be comfortable. Their Star Mobil system is a series of lightweight, interlocking, nearly flat plastic springs that come in different configurations and support the mattress above, while providing ventilation below.
The different sizes and shapes of the units are meant to accommodate different body weights and even areas of the body (i.e. the shoulders and hips require more "give" than the waist and legs). Thus you'd use more than one type of Star Mobil unit to make up your grid.
You can also configure the grid for irregular shapes.
"The spring elements are clipped into a comfortable spring base (slatted frame) with 3 different hardness zones. The body is positioned correctly orthopedically and receives individual and pressure-relieving support. In this way, tension and one-sided loading can be avoided. Open, air-permeable cells ensure perfect ventilation and an optimal sleeping climate."
The system comes to you in a box, and here's how you put it together:
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Here's an in-depth explanation of how the springs are differently tuned. (It's in German, but you can turn on the English subtitles, which have been properly translated.)