Please help me in building a cornice board. I have vertical blinds (including the header). I want to leave these up and build a cornice board that will slip right over the header. That way I can use the existing supports and hardware. I will be padding and wrapping the cornice board with fabric. The width will be about 65". I need to use something lightweight for the board. What material could I consider and what type of nails/ clue etc. would I use? Thanks for any help you can give me.