I've got my 2 layers of micore cut and fit to the raised hearth I built today for my NC13. I plan on going the micore, micore, durock, to get the R value I need. I don't have the Durock cut yet. My questions are these........ 1. Do I secure each layer of micore individually, or wait until I fit and cut the Durock, and secure all 3 layers (micore, micore, durock) together with the 2.5" Durock screws??? 2. Should I use any construction adhesive between the deck/micore, the micore/micore, or the micore/durock???? Thanks in advance!!