The front living room in our 5er has 2 opposing couches that fold out and almost touch each other in the middle, making one gigantic bed across the entire front of the 5er. Problem though, those fold cracks are very uncomfortable. Solution?
We purchased 2 air mattresses (with electric pump) to lay on the top of each bed. Worked pretty good. My wife and I slept on them to test them out completely. We did not feel the cracks at all. The air mattress was an 8 inch deep one. If you used the 12 inch deep one, you'd do even better.
The only problem was, I don't sleep well on air mattresses. But the problem with the cracks was definitely not the issue any more.
We eventually went with stuffed mattress covers that resemble a fitted sheet. That also cushioned the crack and finally had comfort.
We don't sleep on them, but we do pull them out and lounge around on them watching television. My son and grandson sleep on them when they come with us. Quite comfortable now.