Starting search, side sleeper with lower back issues

I've been on Ther a pedic Tri-tec 2000 with wool comfort for about 9 years? It has had the sag in the middle for awhile which isn't so so bad but now its starting to
give me hip pain. I have been content enough with it though.
I'm 58, sleep alone, side sleeper who really wants to be a stomach sleeper but can't anymore:). I have lower back issues with a chronic herniated disc thing. My hips are starting to bother me. I weigh about 200 lbs. I tend to sleep hot.
I have always had a thing where I hug the sides of the bed, facing out. The sides always feel better. Maybe I like sleeping on a slight uphill? Don't know what that means, if anything but thought I'd mention it.
I will be buying a full size mattress. I travel from side to side to turn over and sleep facing out a lot and if it weren't for the pets honestly I'd probably get a twin.
I will be placing it on a decent quality slatted futon frame on top of the the thin (3-4") cotton wool futon which is what the Therapedic is on. I don't feel that I need a special mattress to do this as the current mattress is not.

I tend to sleep hot so I have never investigated the memory foam thing. I also start switching sides about every half hour about 3 hours into the night. Yes I sleep like crap but I don't think or expect a mattress to solve that. I just don't want to fight a mattress when I'm trying to turn over. So unless someone has insight I think memory foam is out.

Which leaves latex and coil variants.

A long time ago on a different mattress, before toppers were widely available I got a 2" latex topper on line at a premium site. It seemed very hard and I took it off. But honestly I don't think the experience was the end of the line I just don't know how to evaluate something with so many variables that I have no experience with.

I was talking to a retailer on the phone about chairs and mentioned I would be in the market for a mattress. He mentioned Kingsdown which I had never heard of. He said they have some sort of machine you get on which tells you what kind of mattress you need. Any thoughts on that?

I don't expect something to last forever and don't mind paying for some quality.

Suggestions? (Specific better than general).

Thank you

Mary

You have provided two very solid reasons Not to purchase a Memory Foam Mattress, 1). Hot Sleeper and 2). ability to roll from side to side easily. We have a Tempurpedic and found it difficult to move at all and way too hot. We have found a temporary solution by placing a Wool topper on it under the mattress protector. This has made it a little firmer and also a bit cooler. Duane has talked about Royal Pedic as a brand that he and his entire family use. You might do a web search on that brand and learn something about it.

I find it humorous that some maker has developed a gimmick machine to tell you what bed you need. That's hilarious. Ever wonder what ever happened to those snake oil salesmen from the 1800's and 1900's? They went into the bedding business. There are more false claims and smoke / mirrors in the bedding business than any other aspect of the home furnishings industry. My thoughts on bedding are well documented here, read back into the forum if you like and you will find them.

While I was out I sat on a Therapedic? Memory foam - don't like the sinking slow down thing at all. Nix.

Laid briefly on a Jamison latex on foam. It felt nice. IDK I think he said it was semi firm plush or something? The thing about latex without having actually lived with it - is the soft edge/sides. Sort of bugs me.
I like sleeping hugged up to a side facing out. Don't like facing into the bed, not sure why. Maybe its a habit from liking the firmer sides of coil beds but the idea of a soft edge....
I wonder if I could get used to it.