I’m undecided whether to purchase the topper because:
Not sure if the combination of the memory form and Latex topper (I don’t think the latex topper has enough friction to not “slipping” off).
If the topper can help me stay “cooler” and increase durability of the foam.
I’m a side sleeper and prefer firmer one, though I purchased the CoolComfort the with the default 30/35 core, versus 35/40 core. If I go with the topper, I’m not sure whether to go with the plush or the firm topper since the preference for side sleeper on the comforter level is the “softer” one.
Rocky Mountain also sells a natural talalay top latex mattress (7"/9"), so not sure why they don’t offer Talalay top versus Dunlop one.
These types of questions that are about the specific needs of a customer considering a particular material or about choices that are offered by a particular manufacturer or outlet are usually best addressed on a phone call to the manufacturer themselves because they have a much more detailed knowledge of their specific materials and experience with thousands of customers that will help them be more accurate with specific people/material combinations.
I can give you some generic comments though that may be helpful.
Raw latex that is inside a mattress cover is a very “sticky” material and doesn’t tend to shift. Even with a topper that is covered … it tends to stay in place well with sheets and a protector over it and is easy to adjust if it “pulls in” to the middle over the course of the night.
As to the “feel” of latex over memory foam … this is a combination that I personally like in some cases depending on the type and thickness of the layers. Any material over memory foam will “slow down” the response of the memory foam because it will isolate the memory foam more from body heat. The thicker or more insulating the layer over the memory foam … the more it will affect it and either “firm it up” or “slow it down”. This is one of the reasons I like latex over memory foam because the latex surface is a faster response and the memory foam under it is a slower response which slowly sinks under the latex. This is personal preference though and others may not like this at all (and I still prefer all latex overall for other reasons).
The deeper in a mattress a layer is … the less it compress and be stressed over the course of the night and over time and this will lengthen the life of the deeper foam. Any topper for example will absorb some of the compression from the people sleeping on the mattress and lengthen the life of the materials under it. In the same way a layer in the middle of a mattress will tend to be more durable than the same layer in the top layer of the mattress.
Latex is typically cooler than memory foam and Talalay is cooler than Dunlop but where they “rank” depends on the specific qualities and firmness of each foam, how deeply you sink into it, on the material that covers it, and what is above and below it. More breathable materials or phase change materials in the cover (such as coolmax) can also help regulate sleeping temperature even for foams that would otherwise sleep a little warmer and the closer these are to the body the better they will work. Each piece of the “heat” puzzle will have an effect in combination with the others. Aerus is among the most breathable of all memory foams though so it would be more closely comparable to latex than other memory foams but in most people’s experience latex would still be cooler.
I would not buy a topper with this until I had a chance to sleep on the mattress and see how it interacted and how close it was to your needs and preferences. You already have a 4" comfort layer using a combination of memory foams which may be fine by itself both in terms of temperature, pressure relief, and feel. Only your own personal experience will tell you how far away from your “ideal” you may be and what type of topper has the best odds of getting you there if you should find you need a topper.
I really don’t know how they choose the products to carry but you could ask them and if enough people requested the same thing perhaps they would carry it to satisfy demand. In the meantime there are good quality/value sources for Talalay latex toppers for those who want the softer feel of Talalay.
I talked to Andrew @ Rocky Mountain (Dave is out on family vacation) last Friday. Andrew’s been very helpful as well. So I’ll take your advice to try out the memory foam first (Andrew said it should ship out tonight and arriving Friday since I’m in California, and they are in Utah).
And I will ask Rocky Mountain again if they carry Talalay topper, I do prefer softer and cooler topper, versus Dunlop.