I built a pull down murphy bed for a guest bed. The mattress can be a maximum of 10" high to allow the bed to close properly with bedding in place. The mattress sits on a plywood base so I need a mattress that doesn't require the extra give of a box spring.

Any recommendations?  Unfortunately, I don't think I could build a multi-layer bed because it would fall apart when the bed is in an upright position.

Wow! I'm impressed that you actually built your own Murphy bed. How cool is that!

It may actually be possible to build your own foam mattress for use with this system. Just use two mattress pads. One that goes on the bottom of the mattress and another that slips over the top. If you wanted to secure it even further all you would need to do is add a few stitches here and there to hold it all in place. To keep the weight down I would suggest using a 6" HR base of at least 35 ILD. Add 2" of 20 to 26 ILD latex (depending on how soft you like your comfort layer) or 2" of 4 to 5 lb memory foam if you prefer and you should have a really nice comfy mattress for your guests.

Despite one of the mail order stores telling me there was no problem using a latex or memory foam mattress in a Murphy bed -- it doesn't work very well. I got a latex mattress and it sinks towards the bottom and bunches up when the bed is in the upright position.