7 Zone mattress

Hello

I’m a little unsure where to direct my question but
I’m from Australia and have been looking for a new king mattress, I’ve been constantly coming back here for tips and knowledge and it’s helped out alot

Info
Im 6.3ft and 163lbs and my partner is 5ft and about 167lbs
We are both side and back sleepers

I have scoliosis and have been struggling with the mattress we have now which is spring 8.5inch high with a 2 inch memory foam topper and I find it to firm, i either wake up stiff in the back or back pain in between the shoulder blades, I get alot of pressure on my hips and especially my shoulders

I have decided to go with a latex mattress and have gone with a dawn latex mattress dawnlatexmattress.com.au/

It is a king 8.5inch thick mattress the layers are 2inch soft, 4inch medium and firm (top to bottom, unsure of all measurements) under a cotton cover quilted with Tencel

The owner has recommended 8.5inch instead of 6.5 inch due to my partner being shorter, he said he will custom make it so we have the 3 layers and can change if need be, we are unsure what firmness we want but probably medium soft for $2085

He has also said we can go with 7 zone support for for an extra $440

I understand its personal preference when it comes to these things but I was just wondering if it’s worth paying for the zones if its going to make a difference

He’s been really helpful and from what I have learnt it sounds like the right set up but just unsure of the benefit of zoning especially with height difference between us, my hope is for a soft but supportive firmness

I understand its hard due to me being in Australia but would appreciate any advice!!
Thankyou

https://uploads.mattressunderground.com/outside/45780/Screenshot_20200731-015710_Firefox.jpg
https://uploads.mattressunderground.com/outside/45780/Screenshot_20200731-015349_Firefox.jpg