Hi Aus10sntx,
Welcome to our Mattress forum :)! Thank you for your post and I am sorry to hear about cancer in your ribs, and all the sleep difficulties you’ve had since your surgery. That is really tough during recovery.
Yes, it is always advisable to ask for the density / ILD information, so one can determine if the specifications have the right durability required. Additionally, it is good to know if the retailer/store will be forthcoming with this information. Cantwell Mattress company does have an excellent reputation in the SA area, so you should probably call or email them for this information.
The innerspring that is not pocketed coils will still act a very durable support core for a mattress. It is nice they have their guarantee and they will work with you on the different firmness’s.
There are a number of our Mattress Experts that offer pocketed coil mattresses, and many have a variety of latex comfort layers used on top of the coil base. Luma Sleep has a Natural Latex Hybrid Mattress where you can exchange the top 2" latex layer for free during the first year. The Nest and Ghostbed, in addition to the Luma Sleep, are excellent choices and you can find these in our list of Mattress members and you would also get a very good quality/value for money in an “apples to apples” comparison. Of course, these, like most online retailers, you can return for a full refund if you are not satisfied.
Generally speaking, the graphite infused latex will be of the same general quality as regular latex. But more importantly, what is the ILD/density of the graphite latex. Is it a Talalay or Dunlop process? Supposedly the graphite will help wick moisture away, and it also helps with passing the FR regulations, as it is not as flammable as regular latex. That said, not sure you will notice any of the benefits as this layer is below all of the quilt material.
You seem to have done quite a bit “due diligence” with testing and researching your options. It’s great that you’ve determined that you’d like something with pocket coils for you and your husband and I can certainly understand the sense of overwhelm with thousands of posts on the forum but I’d keep in mind that most of the mattresses you’ve mentioned have different designs and materials which in addition to ILD and density will also introduce more variables for your consideration. (every difference between two mattresses can either have a cumulative effect or an offsetting effect that is very difficult for even a knowledgeable and experienced online manufacturer or retailer to predict how will play out for each individual.) While we are always happy to help with “how” to choose and to act as a "fact check …. in terms of “what” to choose of either a mattress or the balance between comfort/pressure relief and support/alignment that may be suitable for a specific person is always up to the only person who can feel what they feel on a mattress and best left to personal testing and experiences or more detailed discussions with the more knowledgeable people at the retailers or manufacturers that sell a mattress you are considering.
Yes you are correct that higher BMI ranges will need more durable materials and components in a mattress and in a BMI range of 30 or higher I would include any 4 lb memory foam or 1.8 lb polyfoam as a “lower quality/density” material (relative to a higher BMI only) and minimize their use to a total of “about an inch or so or less” in the mattress. For memory foam (or gel memory foam), if your mattress is one sided then I would make sure that any memory foam is at least 5 lb per cubic foot. If the mattress is two-sided then I would use a minimum density of 4 lbs per cubic foot, according to the mattress durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress.
There are also a number of forum posts and threads about mattresses and higher weights and a forum title search on heavy (you can just click this) will bring up many of them. Some examples include the Latex memory Foams for heavy weights people in post #2 here and post #2 here and mattresses for heavy weight people topic here and Best Mattressess for Plus size people Post #3 here has more information and suggestions about heavier weights.
Again the best suggestion I can make (if you didn’t do this already) is to read through How to find the best mattress for you in post #1 here and the information it links to which will give you the basic information you need and will save you having to sort through all the information overload on the forum. And act as a reference to help you make good choices that are suitable for your needs and preferences
Once you’ve had a chance to reassess and narrow your options let us know you have any more questions.
Phoenix