Hi zexpress,
A latex over pocketed spring configuration certainly is a popular combination, and many of the experts I know within the industry, who can sleep on anything they desire, prefer such a configuration. Of course, as I always advise, their opinions and experiences would have no bearing on what works best for you. You should instead reply upon your own considerable experience with different mattresses and components and how you’ve reacted to such products.
Latex would be a more resilient material than memory foam, and it would seem to address some of the complaints you’ve made about memory foam and more than likely sinking in too much for your low back to feel comfortable.
A polyfoam core will tend to be more point elastic than a pocketed innerspring, but both will contour well. The pocketed spring will have a more “flat line” response curve than the polyfoam core, and it will absorb more energy (be more resilient). How a pocketed spring unit contours can vary widely, depending upon the configuration (three versus five zone – please see the article I linked to in my earlier reply about that as the hip region is treated differently), number of springs, thickness of steel, overall profile, etc. And as you mentioned, using such a spring unit can allow for you to reduce the amount of foam comfort material, replacing it with something not as thick and also more resilient.
Yes, I would certainly look for something that is customizable, and definitely seek the advice of any manufacturer you’re considering regarding spring unit zoning (if offered) and ILD of the comfort layers offered. There are quite a few forum members who have expertise in latex/pocketed spring products, and I’ve put a listing together of them in this post (along with a few others). If you do eventually decide to purchase from a site member, don’t forget to ask for or use your TMU discount code for that manufacturer.
Phoenix