Hi PepperGrower,
The short answer is ‘it depends’! While larger sized sleepers may want extra layers, a lot of this is down to preference…4" or more on a comfort layer suits some folks, while others prefer of need additional support in more of a transition layer. Again, you want to make sure the top layers are not too soft and allowing you to sink in, but it’s different for every person - even someone with your same size, age and Stats may find a mattress you think is too firm to be too soft. And you can ‘mix’ foams and latex rubber in your comfort layer(s) as well - just keep in mind the foam density recommendations I noted. You also might want to review the You may want to take a look at the Mattress Specifications You Need To Know and see how they compare to the Mattress Durability Guidelines…latex is one of the most durable materials you can have in a mattress but the feel is not enjoyed by all sleepers, so, again - a matter of preference! As long as you have good support and sufficiently dense foam, either can provide a good solid sleep solution. I would say you likely don’t want a mattress height over 13 or 14 inches, but you should continue testing your existing layers, and consider your next step. A DIY Mattress build can be very rewarding as you can zero in to your exact support needs and comfort preferences, but it can be frustrating as well if you need to switch around or exchange/replace/add layers. Keep note of how your shoulder feels at each step, and have patience, soon enough you should have your ideal mattress!
~ Basilio