I’m planning to go old-school futon in mine. I haven’t tried it yet, but I think a queen sized futon will fit with just a bit of reshaping/ shifting of the stuffing to get the fit right in the corners. Looking at getting some 2″ EVA foam to provide some insulation and a little cushion, and putting the 4″ futon on top of that. $350 total for all new, quality materials.