Our PU came with mattresses that are just thick foam pieces, but I would like to replace the mattresses with something new. I've found the Zinus 4" mattress topper that looks like it's just a thick piece of foam. Can I use JUST that as a mattress? This is the link: https://www.amazon.com/gp/aw/d/B071ZTK34B?th=1&psc=1 Or I was looking into this mattress: https://www.amazon.com/gp/product/B...09-20&linkId=8047aa2728f7a6c9b2c227e33f04716a I was worried about price at first, but I think we may just replace one now and use our air mattress or a pallet for the kids while we try to space out the cost of our renovations/modifications. I still would like to do this as cheaply as possible, but I also want to sleep well!