Hi jleining,
It’s not normally an issue if you are in a reply window but it can happen occasionally with any forum software when there are a combination of factors that can cause your current forum session to time out (see post #3 here).
You can see some comments about solid surface support systems in post #10 here. It would certainly be supportive enough and if you don’t have any additional risk factors it should be fine. With a bed rug to provide some additional airflow and breathability under the mattress it would certainly be fine in any normal conditions.
The thickness of a mattress or the number of layers or the thickness of any individual layers inside it is really just a side effect of the design and the design goals of a mattress and the thickness of any individual layers or the complete mattress is also only one of many variables that can affect the feel and performance of a mattress relative to any particular person (see post #2 here) and by itself isn’t particularly meaningful (see post #2 here). In some cases people that are in higher weight ranges (or a higher BMI) will sometimes do better with a mattress that is thicker than lower weight ranges or a lower BMI (see post #14 here for more about the effect of thickness) but even this depends more on the specific design and combination of materials in the mattress and on how well your testing or personal experience indicates the mattress “as a whole” matches your specific needs and preferences in terms of comfort, firmness, and PPP than it does on just the thickness itself.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart (and isn’t just interested in “selling you” any mattress they can convince you to buy) and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Both of the manufacturers you are considering are members here which means that I think highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency so you are certainly looking two great quality/value choices.
Once you have narrowed down your options to a list of finalists that are all choices between “good and good” (which you have) and you have confirmed that none of them have any lower quality materials or “weak links” in their design (which they don’t) and if at this point there are no clear winners between them (which is usually a good indication that you have done some good research) then you are in the fortunate position that any of them would likely be a suitable choice and post #2 here can help you make a final choice based on your more detailed conversations with each of them, your personal preferences, your confidence about PPP and the suitability of each one, their prices, the options you have after a purchase to fine tune the mattress or exchange or return the mattress (or individual layers in some cases) and any costs involved, any additional extras that are part of each purchase, and on “informed best judgement” based on all the other objective, subjective, and intangible parts of your personal value equation that are most important to you.
Phoenix