Myrbacka latex (ikea)-attempting to replicate

Of all things, currently we attempting to replicate Ikea Myrbacka Latex. Been doing surgery on it. We were gonna pitch it because it was way too hot, but after removing case-we rethought everything.
Need some assistance.
Original cover was making it too hot, so we currently have mattress encasement off & have cotton quilted mattress protector on it.
We decided this level of firmness, whether the mattress encasement is on-which makes it firmer, or off, which makes it more plush-this is the best support for the both of us. It is 8-10 yrs old & nearing the end of it’s useful life, some crumbling is beginning around the edges…It appears to be 5-6 inches of some type of latex glued to a 2" polyfoam base. No polyfoam for base replicated the feel, so that is out.
We’ve played with multiple configurations of various polyfoam ILDs, latex toppers & covers, and here is the closest so far:
We have found that 2 SOL 3" firm toppers, with their cotton stretch cases on our sweetspot-VERY close to what the myrbacka felt like NEW and in the case as far as support.
We are trying to dial in the uppermost layer. We tried a 3" SOL medium, but it feels way too soft & had no support, just bottomed out (felt like a 10 ILD 1.8lb polyfoam no matter what we did with it, including folding it in 1/2 & trying it as a 6").

I’m looking for a medium that feels medium, if this makes any sense. We are burnt out. If I were to compare the feel we are attempting for the topper needed, I would compare it to a 2.6lb 25-28 ILD polyfoam.
I know everything will firm up in a mattress case. We are considering getting a 6" case from APM to protect the 6" of SOL firm, since it is perfect, & placing the topper on top of that case, so it can be “free” & in direct contact with us.
The biggest issue seems to be the vast difference in what is considered medium, and return policies for toppers. I know many places have latex mattresses to test, wondering if any stores have toppers to test? I’m tired of wrestling with foam & latex at home, have a room dedicated to the cause-not kidding.

@Catia

Hi Catia, I’m so happy I found your post! We’re trying to do exactly what you did: replicate the Myrbacka because we loved it so much when we first bought it but it’s been 10 years now and it’s not as supportive as when we first bought it. What combination did you end up with? And, how close did you get it to the original feel? Any advice?