Hi! I decided to get creative and make a daybed from 2 box springs (the king-sized halves) and want to know the best way to form the "mattress" on top. I was able to use the metal bed frame (w/ the casters) to fit one of the box springs perfectly, and I stacked the other box spring on top. I plan on putting a rug pad in between to prevent slipping, but what I haven't quite figured out yet is how to build the mattress on top so it can actually be comfortable. Should I just get thick upholstery foam and batting? Or would it make more sense to buy an extra-long twin sized mattress (in that case I could make 2 beds, right?) from somewhere cheap? I was originally trying to use it as an extra bed/seating, but it probably won't be used very often, so extreme comfort isn't an issue.