I have been researching Zenhaven since a local retailer said he can get a queen Zenhaven from a comfort return at a price under $1,000. I am thin and a back sleeper with extra curve in my lumbar area, so I need a very supportive mattress. The best I have found locally (with very few all-latex options which my wife wants for chemical sensitivity reasons) is the Pure Talalay Bliss - Nature. The PTB Beautiful was too soft and gave a hammock feel where my lower back sunk down. The Nature was much more supportive for my lumbar area. The Nature (and most other latex mattresses) have progressively firmer layers as you go down.
I am assuming I will prefer the Gentle Firm side of the Zenhaven. I am a little concerned that the Zenhaven has 2 layers below the Gentle Firm support layer (ILD 30-34) that are less firm - Luxury Plush support layer (25-29) and Luxury Plush comfort layer (14-19). Do these layers take away any of the firm support? Do they have any advantages besides just a taller total mattress height?
The Zenhaven is set up as a flippable mattress, with a different comfort on each side, and as such will have the slightly softer comfort layer on the bottom of the mattress as well as the top, much like two-sided innerspring mattresses, where the comfort layers are softer than the central innerspring core. The uppermost comfort layers on the Zenhaven are 1.5”, and the core would be a total of 6" of two 3" layers of firmer latex, and as force is distributed over a wider area in the bottom layers of a mattress (as opposed to being more point specific in the uppermost layers when sleeping upon a mattress), this generally wouldn’t be a concern in the product you described. Both the Nature and the Beautiful use a “progressive” construction, but are also set up to be one-sided, and as such in this case use firmer latex on the bottom of the mattress.
The other thing you may wish to evaluate is that you are considering a used mattress, which in general has no warranty and has also been in use by someone else and in their home, so you’d have to rate your own “comfort” with that type of a product and if it is personally worth the savings you may experience versus a new item.