Hello Jacksonhp9!
Welcome to our Mattress Forum 
Congratulations on purchasing the Alexander Signature Hybrid! :cheer:
I understand your concerns, most people with your body type have difficulties finding the right fit so I hope the Alexander works just fine for you and that you would not need to look into mattress zoning options.
Zoning systems of various types can sometimes be useful and worth considering for people that have more difficulty finding a mattress with the right “balance” between comfort/pressure relief (under the shoulders especially) and support/alignment (under the hips/pelvis especially) or who have more challenging circumstances or sensitivities, body types that are more difficult to “match” to a mattress, more complex medical issues, or who have a history of having more difficulty in finding a mattress that works well for them. You may want to first read this article about mattress zoning and in post #11 here and the additional posts it links to but once again the only way to know whether any specific mattress (zoned or otherwise) will be a good “match” for you in terms of PPP will be based on your own careful testing and/or your own personal experience.
With zoning, you’d need to take into account how your weight is distributed, the distance between the hip and shoulders and where within the mattress you need to position yourself to get the desired alignment and comfort.
I am sure you came across this article already but it is worth reading about innersprings and their differences here it in the context of zoning. Good suggestion from April to look at FloBes options and advice. They are also TMU expert on mattress zoning issues.
I would hold off for a while with selling your DIY components until you determine that your new mattress is a fit just in case things do not turn as well as you hoped for with Alexander Hybrid and you would need to camp on for a little longer on your DIY. Selling a mattress or components on the forum normally requires prior permission (see the forum rules here ) but since you meet all the other criteria I’ve decided to allow it “after the fact” in this case. Usually, interested subscribers would see your post and send you a PM, so you may want to watch your inbox as PM’s do not send notifications.
It may also be worth listing it on Craigslist as well since there are many people that look for used mattresses/components as well
Phoenix