Did this last year and been super happy with how it turned out, so i thought i'd give others an idea.
Thermarest actually makes one similar to this called the "DreamTime" .... but my way is actually more comfortable and way cheaper
This thermarest is the basecamp model that is already 2" thick i believe and 30" wide.
I bought a mattress topper from Walmart (Don't get a full memory foam one, as it tends to squish down to nothing. As you can see this is a hybrid one made of two layers of foam). I think this cost $50, but it makes two, so $25each.
Then i put both into a large fleece sleeping bag liner from mec. This was $49, but i'm sure there are cheaper options. The stuff sack is a large tent bag from WSS at $7-8 or something like that.
I know others use foam on top of their mattresses as well, but they get dirty and look like sh** in no time. So if you're looking to keep them in place and clean, get this sleeping bag liner
- You don't slide as much on the fleece
- The fleece feels nice and is washable
- It weighs probably 12lb so, no, you're not gonna be packing this in
Cheers