Hi jkozlow3,
The Iliac Crest (which is what you are referring to) isn’t an actual zone but can be a pressure point for some people. It is narrower than the hips and would normally be taken care of by the comfort layer and would likely be fine no matter which zone it falls in.
Yes … this would be fine (as long as your platform bed is strong enough for the mattress and the people lying on it and has good center support to the floor). The foundations that Flobeds sells are also slatted and I personally would choose a slatted foundation over a solid wood foundation unless there was a compelling reason to choose otherwise (see post #10 here).
I’ll leave any specific zoning suggestions to your more detailed conversations with them. They would be a much better source of guidance than I am. Don’t forget that they do this every day and you also have the option of exchanging them if for some reason their “best efforts” turn out not to be ideal for you.
Phoenix