I think you definitely need to add a middle layer of medium density foam, somewhere around 25 ILD, which should improve comfort considerably. Before I bought my current mattress two months ago, I was sleeping on a mostly all latex mattress which started failing around 15 years after I purchased it. The bottom layer was 6" of firm latex, the middle layer was 3" medium density polyurethane foam and the top was 3" of soft latex. The layer that failed was the polyurethane foam. So I placed the soft latex layer over the firm bottom layer. This solved the sagging issue and low back pain in the morning, but it was not very comfortable at all. I then placed a medium firmness layer of polyurethane foam in the middle, which made the mattress a lot more comfortable. I continued to use this mattress for another three years, until the top layer and mattress cover failed. You need a middle layer to transition from The firm to the soft top layer.
@gme109: Thank you for the reply, this is very helpful. Since you had experience with both polyurethane foam and latex, what if I add a medium firmness latex instead of polyurethane foam? If they have the same firmness do you think latex would have a different feel (more bouncy?) or there would be no difference through the memory foam top layer? My consideration is that good quality natural latex 3āā layer will probably last longer than 2.6 lb HR foam, which will give me more options in the future. Another thought is that, since Iāve never had latex mattress before, perhaps medium latex layer on top of memory foam might feel better? Any thoughts? Thank you!
I would definitely go with a latex layer. Like you said it will last longer, and it has a better feel compared to polyurethane foam.
Before my last mattress, the one I had for 18 years, I had a memory foam mattress. I still have the components of that mattress, which I barely used because I didnāt like the feel it. It wasnāt a Tempur-Pedic, I believe it was a supple-pedic mattress. The mattress was just too soft and lacked support. It had a 3" firm layer of polyurethane foam on the bottom, a 3" medium polyurethane foam layer in the center, and a soft 3" layer of memory foam on top. I tried to make that mattress work by replacing the bottom layer with an extra firm layer of polyurethane foam, but it still lacked support. One thing Iāve figured out with all of these mattresses is, 3" middle and top layers donāt work for me. A 6" firm bottom layer followed by 2-2" layers on top provide better support for my body. My spine doesnāt stay in alignment with 3" of soft on top and 3" of medium in the middle.