Hey ND Farrier,
Thanks for your response and post updates

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We have had it delivered Nov 18th. It has a body sag that you roll into. It is like the springs are split pulling them both towards the top of the bed and the foot so you have a V that the crease shows. The edges and the top and bottom are nice and firm... but this center canyon hurts on the edge where you fall into it. Almost like if there was a 2x4 edge.
Thanks for the added details regarding the odd creasing shown in your pics. Indeed, those are unusual for a mattress with barely six weeks of use and must be terribly frustrating as well, given that this new mattress is a warranty replacement for your previous Zinus product.
I can not find a corner tag on this mattress at all to check the date. It must be underneath? I tried the pull apart thing but it has not changed. the issue. Still no reply from Zinus customer service to date and I sent the last email to them on 06 December. UPDATED POST: After a thorough search (tag was on the side not the corner) I see it was made in February 2020. That’s a long time to be deformed in a box.
Good work finding the law label and thanks for sending those pics, ND

. The label is often attached to either the header or footer section of the mattress near the fabric cover's seamed area, but there are no hard and fast rules. A 2/ 2020 manufacturing date of an imported roll-packed mattress indicates that it has been boxed and stored much longer than the recommended time for compressed mattresses to decompress and function normally. It is also probably why various mattress decompression tips aren't working for your Zinus. Hopefully you will hear from them soon, they a have California-based distribution center (the tag indicates it was ported there) and many of the state's manufacturers have suffered intermittent COVID-19 related shutdowns as well as routine holiday closures . Have you tried calling? Their number is: 800.613.1225. It would be interesting to hear what remedy they offer.
Regarding the Zinus wood base: The open space between my slats is precisely 2.4 inches and the width of each slat is precisely 2.8 inches. There are 14 slats on my board, and an open space of 3.2 inches between the last slat on each end and the frame. The slats give if you push on them and seem equal and quality.
Thanks too for including the description of your Zinus wood base, sometimes there is a detail lurking somewhere as an indicator of support failure; however, from your rundown, the wood base seems adequate and not part of the problems the mattress is presenting.
Yes I see a chiropractor and masseur regularly for my back. My last check up showed no bulging discs or other obvious issues and right now we are in winter so my schedule is half of what it is normally.
Good to hear that you have regular professional PT support for maintaining good back health, ND Farrier. Hopefully your lighter winter schedule provides some down time for your back to regroup a bit from the stress of the physical nature of your profession.
So I am wondering if it would be just easier to find a firm 12" foam base and go from there with the new topper. Its a shame Zinus will not respond. I'm back to the couch. Off to search for an economical foam slab. Thanks and Happy New Year!
Let us know how things go with your new DIY project and hoping you find resolution with Zinus soon. Here's to resting well and Happy New Year, ND

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Sensei