Seeking mattress advice hypermobility

I am looking for a king sized mattress for my husband (age 31) and I (age 29). I am 125lbs and 5’5”. He is 193lbs and 5’10”. We are both mostly side sleepers, though he sometimes ends up on his back and I sometimes end up on my stomach. I have ehlers danlos, so having a mattress that is supportive enough for my hypermobile joints is especially important. Memory foam puts me in crazy amount of pain (and is way too hot). I have tried talalay and like the way it feels, and I have never tried Dunlop though I am very open to trying new things that might be better than what I’ve tried in the past. My husband is generally pretty easygoing about mattresses, and I’m definitely the tougher customer.

Having a mattress that I can change out parts over time and one that has a good return policy are priorities for me. I’d probably prefer something with at least some latex, but I’m open minded.

Regarding my mattress history, I bought the luxurion hybrid from latex mattress factory a couple month ago and it is comfortable for my husband (and mostly comfortable for me), but it was not quite right so I am planning to return it. More specifically, it wasn’t quite right for my shoulder and also maybe didn’t offer enough support overall for me (that’s my guess, but I’m not a mattress expert). I switch which side I sleep on throughout and I favor my left side. It takes a lot of effort to make sure I’m on my right side enough to balance things out as it feels like some joints around my hips or pelvis might be shifting out of alignment. I do have known SI joint dysfunction but I’m unsure if that is related. I typically just switch sides when I wake up in pain (it’s been like this for years). Before the luxurion hybrid I had a talalay topper on top of an old ikea mattress. The topper made the mattress much more comfortable, but it was never an ideal setup and was definitely worse than what I’m using now.

Any recommendations?

@BackScience