I have the fireplace installed (Majestic 42"). I have the cultured stone for the wall. What I have is finished drywall that I want to put the stone over. Can I: 1.) Put 1/2" Durarock up over the drywall and mortar the stone to the durarock?, 2.) Put the metal screen (Lathe?) over the drywall, put up a scratch coat and then mortar to the scratch coat?, or 3.) Do I need to get rid of the drywall, put up plywood and then do the same as #2? I'm doing it myself, so I would like to go with #1 if possible. Thanks in advance.