I was going to say what Ed said--probably because I learned it from him years ago in one of his videos.
Bob Loveless always used a tapered tang on his knives, regardless of size.
I consider a tapered tang on full tang knives, to be the mark of a handmade blade (because I've never seen one on a factory knife).
Drill the holes in both the tang and the scales before the taper, then reverse taper each scale while in the rough. When the pins line up easily, you have achieved the correct angles. That's how I do it.