Hi DamionThrakos.
Welcome to our Mattress Forum. 
It’s good to know that you’ve found the resources on our site useful in your research so far! It is always rewarding to see how one-by-one consumers are able to make an informed and educated mattress purchase. Days of sleeping on “hand-me-down and cheap thrift store mattresses” are better left behind as they can definitely throw a wrench in the works when it comes to your general wellbeing and quality of your sleep.
I’m 6’4" and around 240lbs and am primarily a back and side sleeper (mostly back)
My Wife is 5’9" and around 200lbs, is primarily a side sleeper, and sleeps like an absolute furnace.
Because of your larger frame and higher BMI, I’d be sure to find out information listed here so you can compare the quality of the materials and components to the durability guidelines here to dismiss any mattress that has lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making a purchase. Because no materials will last as long with much higher weights the quality and durability of the materials and components are even more important than normal. I would base your choices as much as possible on your own personal testing Post #3 here ~ has more information and suggestions about heavier weights that is worth reading.
There are also a number of forum posts and threads about mattresses and higher weights and a forum title search on heavy (you can just click this) will bring up many of them. Some examples include post #2 here and post #2 here and this thread.
With regards to sleeping hot, it looks like you’ve already considered this aspect based on your choice of mattress materials. So I am only reinforcing your choice of Hybrid latex or all latex with a little “sleeping hot” tips. There are many factors that control the sleeping temperature of a mattress and only one of these is the foam that is used in the mattress … particularly in the upper layers.
While the upper layers of a mattress are the most significant part of temperature and moisture regulation … deeper support components that allow more airflow can also have an effect and so innersprings will also tend to sleep cooler than foam support cores as long as the air can ventilate to the outside of the mattress.
In addition to this … the mattress protector you choose along with your sheets and other bedding and what you wear when you sleep will also have a significant effect on temperature regulation because they can either add to the insulating effect or to the ventilating and moisture-wicking effect of your mattress. You can see more about the effect of different mattress protectors in post #89 here.
Bedding made from natural fibers or viscose materials (like bamboo) will also tend to be cooler than synthetic fibers and linen sheets along with silk are probably the coolest of all the natural fibers for those where the sleeping temperature is a main priority. There is more about sheets and bedding in post #7 here. In many cases changing the mattress protector, sheets, or bedding to cooler versions can make “enough” of a difference for many people who would otherwise sleep hot on a mattress.
[quote]'Ive narrowed my choices down to these, but I’m still open to suggestions:
- SleepEZ 360 Hybrid - I’ve seen this one pop up in a few places. It’s quite affordable for us and I like that the top layer is adjustable in case we wanted to switch it up later on.
- Full Latex Split (either SleepEZ or Flexus Comfort) - I haven’t seen any hybrids that come in a Split Cal King and this would let us utilize the two halves of the adjustable base separately. The downside is that we are uncertain how a full latex mattress would feel, I know very little about the specifics of them, and it is quite a bit more expensive than a hybrid.[/quote]
Both mattresses you selected are great options for you and your wife’s specific needs and preferences. Regardless of which mattress you end up choosing, it’s important that you have a detailed conversation with each of the vendors. They are both knowledgeable and experienced online manufacturers that can help with making the best comfort/support choice if they are given your stats and information about your body types, sleeping styles, general preferences and history, some general information about mattresses you have tested and done well with, and any other specific information or circumstances that could affect your choice of a mattress, along with which mattress you may be considering.
Since you mentioned latex hybrids allowing for a split… [SleepEZ allows both customization and split option and Nest Bedding Hybrid Latex maybe also something you want to look into and test locally.
[quote]The final option would be to take the DIY route. I was thinking the 8" quantum edge elite coils with at least one layer of medium dunlap on top, but that’s about as much as I’ve figured for that.
[/quote]
A DIY is certainly an option and can get a bit complex but it is usually a rewarding option if approached in the spirit of adventure. You’d be able to tweak and adjust the mattress to your liking, and can do a side-by-side split if your partner would prefer a different feel or firmness. If that’s the route you choose to take, there are experts and resources on TMU to help, if you chose to go that route.
Here are some slicked experts that can offer personalized guidance on how to do this whether you buy from them or not.
Deborah at DIY Natural bedding
Ken at Arizona premium mattress company is very skilled at helping consumers with their DIY
Shawn and Rodger at Latex Mattress company
And of course, SleepEZ can help with building a DIY as well.
There is quite a bit of info to sift through, and I hope it helps you dial in on the best decision for you If any additional questions arise, I will be here to answer them. I look forward to your updates.
Phoenix