Hi grandeson,
Thanks for taking the time to share an update … and it’s great to hear that your mattress is working out so well for you
You can see my comments about a solid support surface under a mattress in post #10 here. While it’s true that they can add some additional risk in terms of ventilation under the mattress … in most cases if there aren’t any additional risk factors they would be fine. As an example I have an adjustable bed with a solid surface platform under my mattress but I don’t have any other significant risk factors so I personally have no concerns about any mold or mildew issues.
Phoenix