First off, I’d just like to say what a great site this is for mattress info.
I’m planning on getting a new foam mattress after sleeping on springs for many,many years .I want to build my own twin XL. I’m 6’ 2" and 220lbs and a side sleeper. I’ve been recommended to go for 3" each of a XF - F - M build. I’d like to experiment with the top layer by perhaps going with 2" of M and 2" of S instead of the 3" of M for a 10" total instead of the three layers totaling 9". I’ve already got a thick wool mattress cover that I plan on using as well. Is there any problem with the idea of 4 layers vs. 3?
I was also planning on an adjustable bed to read and watch TV only but I just saw something called the Mattress Genie that uses an inflatable air bladder to just raise the head portion of the bed. That solution would work for me and I want to know if there is any negative things I should be concerned with.
In theory no … none at all. You can see in post #14 here that there may be some potential benefits to a thicker mattress for heavier weights or certain circumstances or preferences (assuming that the materials are high quality). I would also make sure that any foam you use is high quality … particularly in the upper layers (although I’m guessing that by “foam” you mean latex?). There can also be some benefits to having more layers to re-arrange or exchange which you can read about in post #2 here although it can also add complexity which can make finding the best combination more difficult for some and there are some combinations that wouldn’t be suitable (such as too much soft foam on the bottom).
I’ve never used it personally but for those that just want the benefits of torso elevation I think it’s a good and economical solution. I’d probably also get a one of their wedges for under the knees so you can achieve the zero gravity position. You can see a comment from someone who used it (and also built their own DIY mattress to match the Pure Latex Bliss Nature and Nutrition) in this post.