First, welcome to the ALR site! You'll likely find that this site becomes as much an addiction as the muzzleloading hobby itself.
It sounds to me as if you may not have quite enough of a step up to the pipe's tang. You do not want more than 1/8" of wood between the rod hole and the bottom of the forend, and as little as 1/16" is fine. In the latter case, you will find that you break through into the rod hole when you inlet the tang of the entry pipe, and that's fine. What you want to avoid is a forend that is too deep vertically...too much wood in the web, too large a rod hole, and too much wood under it.