Hi Steve,
I have copies of all the posts we exchanged at What’sthebest (and I’m sure that they’re not part of the ones they deleted anyway so I could find them there as well) but I’m sure there has been some changes since that time so it would probably help if you brought me up to date in terms of what you are currently sleeping on (and any “spare materials” you still have) and any current symptoms so I don’t have to go over a LOT of old information that may be a little out of date 
Just as a “review” to set the stage for the thread, zoning as you know is to prevent the pelvis from sinking in too deeply while at the same time allowing the shoulders to sink in far enough for good pressure relief. In most cases … higher quality materials can do this without zoning but with more challenging circumstances then zoning is a great option.
With most people … more typical 3 zone zoning works well. It makes the middle third or so of the mattress firmer because the single biggest issue is supporting and holding up the pelvic girdle which is the heaviest part of the body. This allows for the use of thicker softer foam in the comfort layers to accommodate the shoulders without compromising support under the pelvic area. For most people this works well because the thicker and/or softer comfort layers also allows the “gaps” in the body profile to be filled in which gives lighter support under the lumbar in the waist or small of the back area which is not as heavy and usually doesn’t need the same degree of support as the heavier pelvis. Most back pain is when the pelvis sinks too far and the lower lumbar is either crooked or twisted causing lower back misalignment and pain.
In some cases however this isn’t the most suitable form of zoning. The two cases where this is most common is either people who are heavier in the belly/waist area or people who are much lighter.
In the first case … the heavier belly area may weigh down the natural curve of the spine and needs firmer support under the curved part of the lumbar which isn’t able to maintain it’s natural curvature when the sleeper is fully relaxed. This is similar to someone having a mattress that is too firm that doesn’t allow them to sink in far enough to fill in the gaps and the curved part of the spine can “collapse” causing discomfort and pain. In this case a smaller narrower zone with firmer foam or base support under the curve with softer foam under the pelvis and shoulders allows the more protuding parts to sink in deeper and allows the curved area of the lumbar to contact and compress the foam under it which creates better support. By taking up some of the weight of the lower body, this can also help with pressure relief in the hips. This zoning can be either on top, below, or both depending on the degree of zoning needed and the materials and layering used.
The other case where this can work well is with very light people who don’t weigh enough to sink into the mattress enough to fill in the gaps and/or may prefer a firmer mattress. Reverse zoning here allows the use of slightly softer foams under the hips and/or shoulders and keep the firmness under the curved part of the Lumbar so that it can support more weight and is better supported.
Different body shapes can play a role here as well with spines that are more curved having a bigger gap that needs to be filled in and supported.
So strangely enough … Reverse Zoning often works best for both ends of the weight spectrum … either much lighter or those who are larger and heavier with more of their weight in the belly area.
Having said all that … in the case of most zoned latex cores … the zoning typically only has a range of about 6 ILD from the firmest to the softest zone which is very little. This is often less than the normal surface variation of the latex layer itself.
Innerspring zoning can have a wider range and innersprings themselves have a different type of response than latex or foam so this may also be worth exploring (more to come on this later). With latex, zoning may need a manual version rather than zoning built into the layer itself.
So most of this is just to “catch up” to where you are in terms of what you’re sleeping on and an update on your symptoms before I explore more possibilities and turn this post into a thesis (not that that’s so unusual for me :))
Phoenix