Hi tiridley,
You can read a little more about Solstice Sleep Products in post #2 here along with the rest of the topic and the posts and information it links to.
In most cases the retailer would have the best chance of success at finding out foam specs for you (many manufacturers don’t deal with consumer requests for information directly) but in the case of Solstice I wouldn’t be optimistic that you will be able to find them out.
The better options and possibilities I’m aware of in the Birmingham area are listed in post #57 here.
While there are certainly some “legitimate” sales with smaller discounts on holidays … most of the “major holiday sales” with larger discounts are based on fake retail prices and I would treat them as more of a warning sign than something worth waiting for (see point #5 in the guidelines here and post #5 here about fake sales).
I would avoid the temptation to try and design your own mattress or decide on the specs of a mattress that you think may work best ahead of time. Even the best mattress designers in the industry don’t know for sure what a combination of specs and materials they have never slept on will feel like until they try it and they are often surprised at how different it feels in real life compared to the “theory” that they imagined.
Phoenix