Hi dn,
It will be interesting to see the results of your zoning experiments 
I don’t think so either.
If “allowing” your shoulders are the biggest issue then the 1/3 - 2/3 zoning can work well. A good place for the zoning “cut” would be around the area of the bottom of the rib cage (about a couple of inches above the belly button) but make sure you allow for some space above your head in the mattress as well.
As fate would have it … this post from today is from one of the members that had some good success with the flobeds vZone after first trying their non zoned mattress.
Phoenix