At the beginning of the year I had posted about our solution to the storage bin lip, which is about 3/16" higher than the cabin floor. For me, the top edge lines up perfectly with my hip, which was something that became more noticeable as we racked up lots of nights in our trailer and the CI mattress started to break down a bit.
Our original solution was to repurpose an old bicycle trainer mat that protected the floor from dripping sweat when training indoors. This is sort of a thin anti fatigue mat.
As you can see from the above photos, I trimmed it to the width of the cabin, and around the top edge of the storage bins. In our original solution, we cut a second identical mat and placed it over the top, but it was a foot or so lower than the first mat - placed so that it cushioned from my shoulder down.
We recently conceived a need for an additional mat, so we went shopping. Lowes carries a similar mat in their carpet section, though theirs is not as cushiony. I think it was $50 for a 4x8' sheet. But they did have a thick anti-fatigue mat that measured 3x5' for $25 each. We bought two and removed the top trainer mat.
We had to trim about 4" off the long end, and the mats aren't quite as long as the cabin, but they are more than long enough to improve comfort.
These mats are awesome because they add additional cushioning, and they are dense enough that they don't shift around when moving the mattress in and out of the cabin (which is a potential problem with lighter weight closed cell foam, such as backpacking pads).
So if you've had your mattress for a while and are finding that it is not as comfortable as it once was, then definitely give this a try. You'll find it is far more comfortable that the original mattress, with or without an added memory foam topper.
The second trainer mat will now be repurposed as the bottom liner of our dogs new crate that we're building for our new tow vehicle...