Hey Free Spirit54,
Thanks for your reply and updates

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Before I contacted you I spoke to Ken and it was great, he helped me out with my mattress configuration after I explained to him my preferences, so I'm pleased in that aspect. My bed size is Eastern King. It didn't occur to me to ask Ken about coir pads or check if my king size metal box spring complies with the warranty because this box spring says to be "crafted to support any memory foam, spring or latex mattress". The slats size, and the space between them fall into what I have read as acceptable. Also, the mattress will lay on the box spring which come with a thin cover, and the box spring will lay on my bed frame.
Very good, Free Spirit54; happy to hear that you have spoken with Ken regarding your mattress configuration and that you were pleased with the outcome. He has a deep understanding of latex layering construction in regards to consumers' preferences/ PPP and is best suited to answer how which type box springs/ foundations or other accessories would impact the "feel" and performance of his mattresses.
I have attached a picture of the box spring and I will check the warranty with Arizona Premium Mattress, and if I have everything on line, could a coir pad change the mattres configuration to firmer or softer?
Thanks too for the images of your foundation; they are helpful for better understanding your proposed mattress setup. I often mention warranties when asked questions about foundations as manufacturers are specific as to which ones would not provide optimal performance for their products, those details are best understood from the beginning.
A coco coir pad between your mattress and foundation shouldn't change the feel of the mattress setup as you describe but again, I would defer to Ken's thoughts on this as he would have a better understanding of how the materials would interact. To save you the time of a new post, I am happy to send him the question on your behalf. Looking forward to hearing updates once you are on the other side of your new mattress "sleep trial"

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Thanks,
Sensei