Keefer, IMO, That is just the way a selfbow is. It can't be made to centershot, so you must make up for it with weaker spined arrows so they will paradox around the handle and go where you are looking. It takes some experimenting with different spines, arrow length, point weight, etc... You might be shooting too heavy spined arrow that is slapping against your handle instead of bending around it.
I am sure that Mike will chime in here when he gets back, but I am sure that we are not suppose to cut into the riser to make it more center shot(I have made 3 bows from his blanks, two of which are mine and shoot often). Don't cut into it till you here from him.....Terry