We use 4lb density for our overlays. We find that it has the right mix of support, comfort, product longevity, and pressure diffusion.The density (poundage) does not reflect product life or support at all. In fact we used to use a 5lb density foam, but it broke down under body load fairly quickly and was too firm in the cooler months. It all depends on the structure and chemicals used for a particular application of visco elastic memory foam. The one that we are now using does the job beautifully, and we have been using this formula now for over three years and haven't had one back yet, and we have produced and sold more than a few thousand.Let's know if you need to discuss this further with us. But please remember that poundage has nothing to do with comfort, support, and product longevity. Tear strength is the key, and heavier poundages will often break down must faster. That's what we found a few years back.