Hi Sleepygal,
Congratulations on your new mattress first of all 
As you know I think highly of Neal and Spindle and the quality/value of their mattresses and the knowledge, service, and guidance he provides to his customers and I think you made a great choice.
I’m looking forward to your feedback when you receive it and have had the chance to sleep on it for a bit.
[quote]For the base I was really hoping to get the S-Cape adjustable base with massage to manage my fibromyalgia (wide spread muscle pain, aches, fatigue, & unrefreshing sleep) but we can’t afford it (yet). I had hoped for lower Black Friday /Cyber Monday sale prices.
So, My next choice is an adjustable wire grid foundation: Pragmatic-Adjustable-Bed-Frame-Head-and-Foot-Split-King
or like this Primo International Fleet Adjustable Bed Frame Head and Foot, Split Cal King.
Would a layer of firm base foam would be my best solution to prevent sagging and shearing? of the all latex mattress from being on an adjustable wire grid?
What kind of polyfoam?
Do I need closed cell or open cell? (Would closed cell foam would be easier to vaccuum / keep clean?)
What thickness do you suggest?
What Density?[/quote]
You can read a little more of my thoughts about a wire grid support surface with an all latex mattress in post #10 here (which you’ve probably read already).
If you decide to use polyfoam I would use an inch or so of very firm HD polyfoam in about a 40 ILD range or firmer and in about a 1.8 lb density range or higher (for durability). I wouldn’t use a closed cell foam which doesn’t breathe and has a more “pneumatic” feel and is not generally used in sleeping systems. Two inches will do an even better job of isolating and protecting the mattress from the wire grid surface so if the gaps are further apart (only 6 or 7 wires on each side) then 2" may be a little better but 1" would also be fine.
If I was in your shoes however I would tend to use a bed rug which is very durable and more breathable as well but is also more costly.
[quote]About the polyfoam: I went here Foam Factory website and promptly got confused with all the choices, lol:
Conventional Foam Mattresses
Foam Types: Poly Foam, Super Soft Foam, HD36 Regular Foam, Lux Regular Foam, HD36 Foam-HQ and Lux Foam-HQ!
Standard Sizes: Twin, Twin Long, Full, Full Long, Queen, King & Cal King.
Heights: 1/2", 1", 2", 3", 4", 5" and 6"
What foam do you recommend?[/quote]
I would read this post and this post and this topic (about their polyfoam and sources) and this post (presumably from a past employee) before buying anything from FBM. I personally wouldn’t be comfortable dealing with them.
Some of the better online sources for polyfoam that would be suitable for what you need (if you decide to go in this direction) are listed in the component post here.
There will generally be some offgassing or initial smell with any new polyfoam but if it’s CertiPUR certified (Oeko-Tex is not usually a certification used for polyfoam) or if it’s made by a US foam manufacturer (who are almost all CertiPUR certified) then it would be tested for harmful substances or VOC’s and unless you have a known sensitivity to polyfoam even if it’s certified then by most people’s standards it would be “safe enough”.
Phoenix