Hi Thompson,
It sounds like you are on step 3 of the tutorial which is the step where you decide on the local retailers or manufacturers to do some testing so that you can “translate” the information you are reading into personal experience.
If you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of that may be in reasonable driving distance.
If there are few (or no) good local retailers or manufacturers in your area and you are comfortable with an online purchase then the optional online step in the tutorial would replace or be an addition to step 3 in the tutorial. This also includes several links to lists of many of the better online choices I’m aware of.
There is more about the different ways to choose a mattress and how to minimize the risks involved with each of them in post #2 here.
Once you have decided on the types of mattresses and materials you are most interested in and the local or online stores that you are comfortable dealing with then step 4 is about narrowing down your choices to a single finalist at each one (either based on your actual testing or your more detailed conversations with online retailers or manufacturers you are considering.
Unfortunately you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved for anyone to be able to predict which mattress will be the best match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) bases on specs (either yours or a mattress), "theory at a distance, or by brand (see mattress firmness/comfort levels in post #2 here).
Brand shopping is one of the worst ways to choose a mattress and I would avoid brand shopping completely because the name of the manufacturer on a label will tell you little to nothing about whether a mattress is suitable for you in terms of PPP, whether there are any lower quality materials or weak links in the mattress (see this artlcle), or whether a mattress you are considering is good “value” compared to your other finalists based on all your criteria that are most important to you (see post #12 here and post #5 here about “brand shopping”)
There is more about the most important parts of the “value” of a mattress purchase in post #13 here that can help you make more meaningful comparisons between mattresses regardless of the name of the manufacturer.
Phoenix