Thank you so much for this wealth of information.
My husband and I are looking for a new mattress, and I suspect what would work for us is a split queen latex mattress. I would appreciate any advice/help in finding the right configuration.
We have a queen platform bed. We’ve slept on a Tempurpedic 8" mattress for many (probably too many) years. We have resisted replacing it primarily because I am a wheelchair user, the bed height is fixed, it would be very difficult for me to transfer into bed with a taller mattress, and mattresses (as you all know well) have been growing and growing.
My husband has always slept poorly, and increasing age and disability have not improved that situation. He has recently been napping on a 2" closed cell foam wrestling mat in our rec room and reports that he can sleep really well on this extremely firm surface. He is a back sleeper.
I bought a 3" queen size cotton futon from J-Life, and we’ve been sleeping on it for several months. My husband is ecstatic. I am not. I am a side sleeper and need something else. I bought a 2" soft latex topper from SleepOnLatex, and have cut it in half and am sleeping on 4" of topper on top of the futon.
We’re both sleeping well now, but it’s not a good long term solution because a) it’s absurd that my side of the bed is 4" higher than his side and b) the futon has to be folded/flipped/rotated/aired out and a queen size futon is seriously heavy.
Which brings me to the question: what combination of layers in a split queen would give us a similar configuration, and not be higher than 7-9"?
Hi brokenclay.
Welcome to our Mattress Forum. 
Thank you for sharing some of your sleeping statistics with us! Sorry to hear your current mattress isn’t working out for you, and that you’re unhappy with your homemade fix.
One of our Trusted Members, Sleep EZ actually allows you to “build your own” split latex configuration (including queen size). You can input your height, weight, and sleeping position, and it will come up with a configuration for each side for you, or you can choose your own firmness manually. The best part is they offer this for 7" (2 layers) and 9" (3 layers) mattress height, as well!
I don’t usually go out of my way to recommend a specific manufacturer or retailer, but this seems to fit what you are looking for very well.
Also, it’s never a bad idea to have a detailed conversation with whomever you choose to purchase from and provide them with your stats, body type, sleeping styles, general preferences and history, some general information about your current mattress, or what you have tested, and any other specific information or circumstances that could affect your choice of a mattress so they can help you choose which may be your best fit from their inventory.
NikkiTMU
Thank you, @NikkiTMU, for your response and recommendation.
I spent quite a bit of time looking through the resources here, and spoke with several of your recommended vendors at length. We are in the Denver area, and were able to test mattress configurations at the Foam Source, and have purchased a mattress composed of a 6" firm core layer and a 2" topper split between medium (for my husband) and soft (for me). We’re excited to see how it works out for us.