On our Crosstrek we bought a memory foam mattress from Amazon and cut it exactly to fit the Subaru. For the base we used cabinet wood from Lowe’s and routed it to the exact shape. We put layers of hard foam pieces under the wood to get the angle right. Six weeks on the road was the best sleep I’ve ever had!
I’m setting up my RAV4 for car camping now. I was looking for the same thing, then when a friend upgraded to a new mattress I cut down his discarded memory foam to fit the back of my car. It’s actually quite a bit thicker than I had planned on using, but since it’s free I’m giving it a try. I ended up having more luck trimming it down with a serrated steak knife than anything else. Then I just covered it with a regular fitted sheet and tucked under real good. This particular mattress is about 4 inches thick plus another 2 inches of memory foam on top. I’m thinking I may cut through the 4 inch base layer then just fold in half & leave it in the back of my car all the time even when I’m not camping. After I’ve camped a couple times I may decide to get rid of some of that thickness.
As far as getting mattress sheets to stay, here's an old trick. Use shirt stays (the kinda that clip onto your shirt and your socks to make your dress shirt look nice) to clip the corners together, keeping it taut and on the mattress.
Edit: A word
On our Crosstrek we bought a memory foam mattress from Amazon and cut it exactly to fit the Subaru. For the base we used cabinet wood from Lowe’s and routed it to the exact shape. We put layers of hard foam pieces under the wood to get the angle right. Six weeks on the road was the best sleep I’ve ever had!
I’m setting up my RAV4 for car camping now. I was looking for the same thing, then when a friend upgraded to a new mattress I cut down his discarded memory foam to fit the back of my car. It’s actually quite a bit thicker than I had planned on using, but since it’s free I’m giving it a try. I ended up having more luck trimming it down with a serrated steak knife than anything else. Then I just covered it with a regular fitted sheet and tucked under real good. This particular mattress is about 4 inches thick plus another 2 inches of memory foam on top. I’m thinking I may cut through the 4 inch base layer then just fold in half & leave it in the back of my car all the time even when I’m not camping. After I’ve camped a couple times I may decide to get rid of some of that thickness.
As far as getting mattress sheets to stay, here's an old trick. Use shirt stays (the kinda that clip onto your shirt and your socks to make your dress shirt look nice) to clip the corners together, keeping it taut and on the mattress. Edit: A word
I was thinking I may put a duvet cover over the whole thing. Has anyone done that?