I’m a light sleeper, and any movement by my husband wakes me up. I will also be startled awake if he drops his hand or phone on the mattress because I can hear it through my pillow. We slept on a queen-size foam mattress for 13 years, and now we have room for a king. For purposes of motion isolation, will putting 2 twin extra-long mattresses side-by-side on a super-stable foundation (e.g. the floor?) solve my problem? Would there still be motion transfer if the mattresses are touching? None of the stores we’ve visited have split-kings to try out. I feel like I could sleep on a slab of rock if that were an option, just to not be woken up every time he turns in bed. However, we are leaning towards latex, because that’s what he had before we met and it was super comfortable.
Lulu
p.s. Thank you so much for this site. Every other site I’d checked (from googling “mattress reviews”) seemed more like advertising masquerading as information (with the possible exception of Consumer Reports, but I could only see limited info as a non-subscriber).
Hi yenlu,
Welcome to the Mattress Forum! 
As you are incredibly sensitive, even to sounds, you’d want as much separation as possible, making both your mattress and your husband’s mattress stable. Even if you place two separate mattresses in a very heavy-duty platform bed base, there would still be some ability for motion transfer in the mattresses touching as well as being in the same platform bed base. But this would be a better option than placing two twin XL sets on one king metal bed frame, as that would definitely transfer more motion through the bed frame. Placing both mattresses on the floor should minimize motion transfer, but if the mattresses were touching you may feel that due to your sensitivities, and you may also hear some of that movement depending upon the structure of your floor (concrete slab vs. wood).
Overall, the more separation and the more solid surface upon which you place your mattresses, the better off you’ll be.
And thank you for the kind words!
Phoenix