Very simple design, that is going to be sharp when you are done, less is more. To get the walnuts to line up just use the fact that you have two strips between the walnuts at the center, so put two strips up front temporary with hot glue or if they are staying then permanently. They should line up if the strips are the same width. In the end your eye is the best measuring device, if it looks good then it's right.

Dave g