How large a contour for this stock

I bought two of these left hand thumbholes for right bolt stocks a few months back for about $58 a piece unfinished. http://www.stockysstocks.com/servlet...le-LEFT/Detail They are made for sporter contour barrels and I was wanting to use the largest contour barrel without having to sand down the barrel channel rails to a complete taper at the end. I know most out there probably don't have this stock but was thinking some of you out there have used other Stockys stocks for sporter weight barrels. What number contour in a Pac Nor or Shilen etc have you selected.