Jerry,
What I'm basically saying is that the web is more or less uniform thickness along the bottom of the barrel. The groove and hole generally follows the barrel contour. As I said, this becomes more critical as the amount of taper on the barrel increases. On a fowling piece with a large breech, as is common on some English examples, it is a necessity unless you want the forestock to be huge. This is how original fowling pieces I've studied were built. On a rifle barrel with considerable swamp, it makes a big difference as well. The "woodsrunner rifle" barrel is a good example. If these measures aren't taken, the stock becomes taller, in the middle sections of the forestock. When doing a rod groove and hole like this I've been using about 1/8" web along the length of the barrel. As I mentioned, I think this method is pretty typical on English and European examples to deal with big breeches. In talking with Wallace, he mentioned the fact that many longrifles he's examined have a uniform web thickness along the ramrod groove as well.