Phoenix - I got a BB BME and am trying it while deciding whether to return or fine tune my other mattress that had the missing latex. I slept on it last night and it had none of the heat issues for me the Restonic did (knock on wood). However, it’s a standard 9-10 inches, and I’d gotten used to the 13" of the Restonic. I liked that I could jump onto the Restonic and not feel the bottom. Just wondering if you have ever heard of adding a bottom layer of foam, basically making the core a little deeper? For instance could I get a 3" piece of very firm Dunlop or very firm foam to put under the BME to add that extra bit of support and depth, that may in practice be felt, more in getting on and off the mattress, rather than while lying flat?
Hi AT,
Congratulations on your new mattress 
As you know the BME is a great quality/value choice and it’s good to hear that it is working well for you in terms of temperature regulation as well.
I’m not so sure that you would “feel” an additional 3" of foam material underneath your mattress (although this would depend to some degree on the body type and sensitivity of the person and on the specifics of the material and the firmness that you were using) or that it would add any additional “support” (if the material provides additional flex under your mattress in some cases it could have a negative effect on the support of the mattress) and I’m also not so sure that I would add anything under or over a mattress based on how it feels when you jump on it vs when you are sleeping on it.
Having said that … if some additional height is important to you then you could add a taller foundation, you could add some risers under your bedframe (see some examples here), you could add some taller legs directly under your foundation (see some examples in post #8 here), or as you mentioned you could also add a foam layer (I would probably choose polyfoam) under your mattress.
If you do decide to add a polyfoam layer I would probably try using the firmest polyfoam you could find (the firmer the better so it has the least possible amount of flex and the least possible effect on the feel and performance of the mattress) and add a cover to it for appearance and put it in between the mattress and the support system (foundation or platform bedframe) under your mattress.
Some of the better online sources for polyfoam I’m aware of are listed in post #4 here.
Phoenix
Is your mattress on a box springs, a foundation, or simply slats sitting on the frame? If on slats, besides adding to the mattress, which yes, people do and besides adding risers, which I have seen make metal wheeled legs bend under the weight, you could add height to your slats by purchasing a foundation. A foundation is simply slats elevated on a box to give you the same height and look as a box spring, just no springs. Like this one and ones that are linked to elsewhere on this site.