Minimum concrete thickness for HDA anchors

I am planning to use HDA-P anchors for an overhead installation. The slab that I am attaching to is comprised of 9" of reinforced concrete, covered with 6" of unreinforced concrete fill, then 2" of finish material. Size M12 anchors are right at their capacity, with tension failure modes of concrete breakout and pryout. I would like to go up to size M16, but it requires a minimum concrete thickness of 10.625". Can I include the 6" of unreinforced concrete as part of my overall thickness, or am I restricted to the 9" reinforced slab?