I want to put in new pine plank flooring in an old farm house. There is currently a plywood (particle) subfloor. Since I don't have a lot of clearance for the doors can I lay down the new flooring ontop of the sub flooring (with a thin insulating layer of cork or wood fiber in between? Will it work to nail the planks into the particle plywood (hidden in the tongue and groove)? Do I need to creat an air space between the 2 layers? Any finishing advice, wax, varnish paolyurethane? Thanks.