If the bed is not a standard twin, wbucket did you use for the mattresses? I live this idea and think you did a supercalifragilisticexpialidocious job. We live in a tiny apartment in Honolulu for most of the year and this would be an bacon solution to an issue I am facing at the moment
That's why I used the Ikea dimensions. I bought the mattresses there, but I guess that won't be much help for you. I doubt there is an Ikea store near you. But maybe you could buy them online. It might even be possible to buy a simple foam mattress and cut it to size.