Hi Traveler471,
Diamond mattress is a regional wholesale manufacturer which is making some very nice quality mattresses. They also have a very informative website with some good information about the materials and construction methods they are using in their mattress lineup. The house brand at Jeromes may or may not be identical to the brands on the Diamond website so a layer by layer spec sheet is always important when you are considering a mattress so you know what materials you are payng for.
Dunlop is a method used to manufacture latex foam and not a mattress brand. There is also quite a difference between Dunlop and Talalay latex even though they are both high quality. The lady you were talking to clearly doesn’t have a clue what she is talking about and if this information is coming from her rep then they don’t have a clue either … but this is not uncommon when you are dealing with a chain store.
I would suggest reading this article which has some guidelines that should help you avoid these types of outlets and the major brands which cater to them.
I would tend to focus on local manufacturers in the area or sleep shops that carry locally made mattresses (like the Diamond) as they will usually be the most knowledgeable about the materials in a mattress and what type of mattress would best suit your needs and preferences. They will usually have the best quality and value as well.
Normally thinner people will use thinner comfort layers as they don’t have as many “gaps” to fill in. In terms of softness I would tend to go with your personal experience in terms of what relieves pressure and keeps you in alignment as there are some thin people who prefer softer than normal comfort layers because of their lower weight (which sinks in more easily to softer foam) while there are another group who prefer a little firmer than normal because of their narrower profile which doesn’t need to sink in as much to relieve pressure. It would depend on whether you like to sleep a little more “in” or “on” a mattress and on your weight distribution and preferences.
There are a few options in the San Diego area in post #2 in this thread
Phoenix