Adding 2 layers of 1 inch poly iso to my roof, In Southwest Florida, was looking to find out what the fastener pattern would be for the second layer of plywood decking that is in a HVHZ, and do the fasteners have to go into the trusses or just 3/4 to 1 inch into the deck.

Layout of what I am doing
1/2″ plywood decking, is original, has already been nailed down at approx. 6″ on center as per code requirement
Synthetic Underlayment Feltbuster
2 layers of 1″ AC foam II from Atlas with staggered seams which from what I can find just needs to be held to the deck with 5 fasteners with washers at the corners and 1 in the middle
5/8″ plywood decking to top off, in order to install a metal roof
Layer of SA underlayment
Layer of the Cedar Air Mesh to help reduce the thermal bridging to the deck under the standing seam metal roof
Then the Metal roof

Any help would be greatly appreciated, can not find a definite answer on the spacing and fastener type for the second layer of plywood