Hun we use the ones that came with it, and then we have put those flat camping mats underneath to block the cold (although soon we will be wanting it cool!) I would be getting thick density foam mattresses cut at Clarks in the right thickness that you need. Otherwise, we also have some Dune 4x4 mattresses that we use in the tent for people, they are super awesome comfy, they are self inflating with a section that is foam, they would probably be the same thickness as what our van mattresses are? They sell them at Anaconda, might be worth checking out..