Hi bmark,
Thanks for the more detailed feedback about your experiences. A few comments ...
First of all ... the Duro-Med topper uses 3 lb foam which is high quality and which would be softer than it's ILD rating because of the convoluting but then get more rapidly firmer as you compressed into the non convoluted part of the topper. Unfortunately they don't provide the ILD but it would be reasonable to think it was firmer than the 19 ILD Talalay. This is much higher quality and density than the other two polyfoam toppers you have. It would act relatively similar to latex in terms of how supportive it was (how quickly it became firmer with compression) although it may start off firmer than the latex as well.
1) I have tried all of these on the Pamper at once, 2" PLB topper/2" Duro-Med egg crate/1.5" zoned poly foam/1" cheap foam pad. And still didn't get comfortable pressure relief and ended up with sore back due to poor spinal alignment (yard stick trick).
Quite frankly this one has me completely baffled. If you were indeed experiencing actual pressure issues on this combination then my "best" suggestion would be that you are very far out of the "norm" because I can't imagine that with comfort layers this thick and soft (a total of 7.5" made up of 1" 19 ILD latex in the Pamper, an additional 2" of 19 ILD latex, the 2" Duromed and then another 2.5" of softer polyfoam toppers) that the vast majority of people would have any pressure points. I also can't imagine that most people also wouldn't have alignment issues with this combination. What I suspect may be happening is that when you are on your side that your joints are stretching beyond their neutral alignment which is causing joint discomfort which may be mimicking pressure issues (such as the discomfort some people will feel if they stand straight and force their hips to move to the side as far as they can). It may be helpful if you let me know where you were experiencing any "symptoms" from this layering but if this really was causing pressure issues then my best suggestion would be to throw away any "theory at a distance" and to personally test mattresses that had known layering until you found one that provided you with good pressure relief and then use that as a "model" for what to do next. The good news is that the other layering you tested is more indicative of what may work for you than this one and have a more consistent pattern.
2)Tried the PLB 2" topper alone, no pressure relief whatsoever, very painful in shoulders & hips.
This makes a little more sense because with 3" of 19 ILD latex as your comfort layer (2" topper + Pamper 1")over the very firm 40 ILD core of the Pamper it still may not have been enough to isolate you from the feel of the firmer layers below it.
3)Tried PLB 2" w/Duro-Med egg crate, not much difference from #1, little pressure relief and bad spinal alignment
This also seems to indicate an issue that is not pressure related because with 5" of soft foam over the support core "in theory" this would also be thick and soft enough to relieve pressure points and once again the discomfort and poor alignment could be coming from alignment issues both in your spine and in your joints.
4)Tried 1.5" zoned pad and 1" cheap pad together, no sore back but no pressure relief.
This would also make sense to me because with relatively thinner comfort layers (3.5") you would be closer to the support core but because they are softer this too may not be enough to isolate you from the firmness of the support core in the mattress (it's thicker than #2 but the comfort layers are also softer and have a lower support factor (then don't get firmer as fast aslatex) so you may well be "going through" these as well.
5)Tried 2" Duro-Med egg crate alone, got some good spinal alignment, and truth is if the pressure relief was better I'd be OK with this step. But eventually during the night, the pressure builds up on the shoulders and causes me to wake up and turn over. Uggh!
Similar comments to #4 and #2. The Duromed is higher quality than the other two foam layers (and likely firmer as well) and is likely providing you with reasonable alignment but still not enough for good pressure relief (this one has a 3' comfort layer)
6)Tried 2" Duro-Med egg crate and 1.5" zoned pad and 1" cheap Walmart pad together, got some OK pressure relief and some spianl alignment problems, but was slightly OK until the two top foam pads became compressed.
Again this seems to confirm the comments about the other options (except #1). It's hard to guess which one this would be most similar to (it has 5.5" in the combination comfort layers) because I don't know the exact details of all the polyfoam layers but it's would be a little more pressure relieving than #5 with the extra polyfoam on top and a little more likely to produce alignment issues because of the extra thickness.
7)Back to the Duro-Med egg crate again, good spinal alignment and initial feel is good, but shoulder/hip pressure builds up. I do like the firmness of this set-up, but got to get rid of the pressure!
Again ... this would be a 3' comfort layer similar to #2 (but the Duromed is likely firmer than the latex) and of course the same as #5.
So with the exception of #1 ... and guessing a bit at the specifics of some of the layers ... most of this makes sense and seems to indicate a "critical zone" or thickness a little more than 3" (say 3.5 - 4") that uses higher quality foam that gets firmer fast enough and has a slightly higher ILD than the cheaper polyfoam toppers you were using.
Do you still have the Duromed topper and is it still in good condition?
If it is ... I would try it on the Pamper and then add the 19 ILD topper on top of this. This would give you a comfort layer of 5" which would be a little on the thick side but it would put the firmer Duromed deeper in the combination and eliminate the cheaper polyfoam toppers.
It would be nice to have 3" of the better quality toppers to play with but it's either 2" or 4" it seems. This combination though is the only one you haven't listed that could provide some meaningful information to the picture. It may also be worth testing it in reverse order to see if there is any difference.
I'm also looking forward to the suggestions of the PLB rep.
Have you tested any of the PLB mattresses by themselves without any topper and is there one that seems to work best for you and doesn't give you a "hint" of familiar "symptoms" in shorter term testing? This may be helpful as well.
Overall I think that the comfort layer thickness that would likely work best for you is in the range of 3.5 - 4" (as much as I dislike being this specific with "theory at a distance" but the trick will be to make sure that all of this is good quality and the right firmness (and again it would be nice to know the specifics of the Duromed).
One step at a time using what you have available ... and if you do decide to give the latex and Duromed topper a try together ... I would give each combination (order of layering) a few days each to make sure that your feedback and experience was more of a pattern than an anomaly.
I would also have suggested the latex topper or the Duromed topper with just the 1.5" zoned topper which would be a little thinner and softer and put you closer to the support layers but your comments indicate that it has compressed already so it may not provide meaningful feedback. I'll leave this up to your best judgement (after the other two options have provided some feedback).
The end result of all of this will hopefully point to a more "permanent" solution that doesn't involve such complex variations where some of the important specs that could be used as a reference are missing.
Phoenix