Hey Dup,
You’re on the right track with your thinking here.
If long-term durability (10+ years) is the priority, I would personally rule out the convoluted HD36-HQ. Even though it’s still a 2.8 lb foam, the reduced material at the peaks changes how the load is carried and concentrates stress in a way that isn’t ideal when durability is the goal. It’s a feel-modification more than a true equivalent to the solid slab.
That leaves you with two realistic directions to take.
A true 28–30 ILD 2.0 lb polyfoam will give you a more intentional “transition” feel, but it is a clear step down in durability compared to both your HR base and the HD36-HQ (if a full slab).
The solid HD36-HQ is the more conservative and durable choice. In a layered build like yours, the perceived firmness difference vs the 34 ILD HR base is likely less significant than it appears on paper once you factor in support factor differences and the latex layer above it.
Regarding ILD’s, they do not translate consistently between foam types, which is why a 34 ILD HR foam can feel firmer than a similar ILD conventional HD foam. HR foam typically has a much higher support factor and more resilient cell structure, so it resists deeper compression more aggressively and “firms up” faster under load. In contrast, standard HD polyfoams tend to have lower support factors and a more linear compression response, so they feel closer to a medium-firm even at similar ILD ratings. That’s why matching ILD numbers across different foam families is often misleading compared to how the layers actually behave in a full build.
A useful comparison is Dunlop vs Talalay latex. Even at the same ILD, Talalay is typically perceived as a bit softer, more uniform, and more “lively,” while Dunlop tends to feel denser and more supportive with a slightly more grounded response. In the past, some of that difference was amplified by greater variability in Dunlop’s density and consistency through the layer, but modern Dunlop production has improved quite a bit in terms of uniformity and quality control. As a result, today’s Dunlop is generally more consistent and closer in behavior to Talalay than it used to be, though it still typically retains a more supportive, less elastic feel due to its structure and processing. The same general principle applies here with HR foam versus conventional HD polyfoam: even if ILD numbers are close, differences in support factor and material behavior mean the real-world feel can be noticeably different, which is why ILD alone becomes less predictive once you start mixing foam types in a layered build.
Latex in that position would be the most durable option of the three, but if you already have uncertainty about the feel, I wouldn’t introduce it into a critical transition layer where you’re trying to control the overall feel of the build.
If it were my build and durability was the primary goal, I’d keep it simple and go with the solid HD36-HQ rather than trying to fine-tune that transition layer too much. The HR core is already doing the heavy lifting in the system anyway.
Hopefully, I have not floated off into lala land, as I sometimes do.
Maverick