If it shrunk 2inches it had to be 4foot wide,whether you mount it or not they will shrink thats the reason you have to let them dry before you get an official score on a rack.1/4 to 1/2 of an inch is more realistic on the inside spread.and a board will work but like someone said it could crack the skull plate I have never saw this but I dont use a board,I have saw people do this.