Hi All
There are different Qualities of Memory foam.
What I would recommend for the Lower foam is ONLY replace the cushion
and the back rest of the back seat. Leave the seat bottom alone.
Replace or skive the foam if you have someone to slice it. The foam
in the back is 4" thick, as with the pad make a 2 inch foam 2235 to
2245 pending your body wt. with a 2 inch topper. Use the FIRMER
memory foam ( sorry can not remember off the top of my head, I think
a 3.2) the 2.8 is softer and will not give the support for a good
night sleep.  Put it in your original covers and seat back and it
will look stock and your feet will not know the memory foam is not
there. You do not want the memory foam in the seat for driving around.
as for the top bunk you have very little to play with. I can not fold
my bunk anymore but at least I can sleep up there without my arms
going numb and hardly able to move in the morning. But upstairs I
used the firmer memory foam on top of a 2245 foam. The base foam will
prevent you from touching the board and the memory foam will give you
support you want.
If you want the 2" memory foam I can order it for you. It is and will
be more expensive then costco. But costco is selling the crappy
memory foam as well. I have the crappy memory foam as well as the
good stuff and there is a huge difference.
The foam is set for me and I weigh 195. If your lighter then you will
have to adjust a bit.
Hope this helps
Jonce

>Back when SewFine was doing my interior, one of the things they noted
>is that the original foam tends to get stiff overtime. They asked if I
>wanted it replaced. I like stiff mattresses, and so didn't replace it.
>
>In other words, instead of getting a topper, you might consider
>getting the foam itself replaced. Jonce might chime in hear with some
>ideas.
>
>On Jul 20, 2009, at 7:14 AM, Richard Golen wrote:
>
>>My wife's back is beginning to bother her when she sleeps in our
>>Westy. Anyone have any recommendations for either a decent air
>>mattress or foam pad that can be used on the lower bunk?