Hi Dale,
We went into Para and looked at all the foam options. We then went around to Bedz -R- Us and found we could buy a standard size innerspring mattress for less than foam. The size we got is a double long. Standard double width, but queen length. We could have squeezed in a queen but the double gives us a bit of space to tuck in the bedding down the sides. And besides it is not like you are going to fall out of bed. We find it to be extremely comfortable and after the one night that we were persuaded to sleep in some one's guest room we agreed that we would never do that again.
The only thing you need to allow for is that you can't fold it up to get it through the door. I have made the lower section of the galley easy to remove so that I can slide it in and out the back. We could have fitted our doors a bit lower as Dale finds that they catch her in the back of the legs. I have longer legs so it doesn't bother me as much, but we now have a couple of small plastic steps and problem solved. And you are going to need steps anyway.

Frank