I don't know when the last time was you slept on an air mattress, but they are cold and it is near impossible to warm up sleeping on one.  The memory foam, on the other hand, is quite cozy once you've warmed it with your body heat.  If you don't use a thick topper it folds in half nicely on top of the back mattress and the rest of the bedding folded neatly on top.  It doesn't need to cover the whole mattress; from shoulder to hip is where you need the cushioning.  My piece is 40" wide by "60 long.

Ellen, Lola and Coee, who in spite of her size is an excellent bed warmer : )

�Be Content with what you have; rejoice in the way things are. When you 
realize there is nothing lacking, the whole world belongs to you.� ~Lao Tzu

> Date: Thu, 19 May 2011 15:06:04 -0700
> From: camping.elliott@GMAIL.COM
> Subject: Re: Sleep Comfort
> To: vanagon@GERRY.VANAGON.COM
> 
> On Thu, 2011-05-19 at 14:21 -0700, Daniel Rotblatt wrote:
> 
> > The only problem with the topper is the room it
> > will take up.
> 
> 
> Seems like a stout old-school canvas and rubber air mattress of the
> right size (if such can be found, we use the lower bunk for sleeping)
> could provide sleepytime mushiness yet pack down small when deflated.
> 
> Has anyone done this?
> 
> --
> Rocky J Squirrel