I previously had a bathroom completely drywalled with DensArmour and now have decided to tile the shower. I would like to install 1/4" Densguard directly over the densarmour and then tile on top of the densguard. Is this ok? If so what type of fasteners to use? roofing nails? duroc type screws? thinset (between the dens armour and guard)?- if so modified or un? or a combination thereof? - or any other suggestions? Thanks for any help or insight.